How Endura Measures Strength

Why Endura’s approach is different

Most strength charts begin with a small group of familiar barbell lifts and reuse the same basic approach everywhere else. That works poorly once you move beyond the bench press, squat and deadlift.

Endura takes the opposite approach. We start with the exercise.

Every tool is built around the movement being measured: its resistance, equipment, execution, available norms and the way strength should scale for that exercise. A pull-up is not treated like a barbell curl. A hack squat is not treated like a barbell back squat. A cable exercise is not automatically treated like a free-weight exercise. A loaded carry cannot be measured properly with the same inputs as a one-repetition maximum.

This exercise-first approach allows Endura to provide useful standards for hundreds of exercises that are usually ignored, grouped together or measured with oversimplified rules.

What Endura tools measure

Endura measures strength in several ways because no single measurement describes every performance.

Absolute strength

Absolute strength is the external resistance lifted, moved, carried or resisted. It is the clearest measurement when the amount of resistance itself is the primary performance.

Relative strength

Relative strength evaluates performance in relation to bodyweight or total system weight. It is especially valuable when comparing people of different sizes or evaluating exercises in which bodyweight contributes directly to the movement.

A basic strength-to-bodyweight ratio is:

That ratio is useful, but Endura does not assume strength scales perfectly with bodyweight. Whenever a more appropriate exercise-specific relationship is available, the tool uses it.

Repetition strength

A set completed for multiple repetitions can be evaluated directly as repetition performance or converted into an estimated maximum-strength value. The right choice depends on the exercise and the question the tool answers.

Muscular endurance

High-repetition tests, timed holds and repeated bodyweight exercises often measure muscular endurance as much as maximum strength. Endura treats these as distinct performances instead of forcing every result into a one-repetition-maximum framework.

Effective resistance

The number printed on a machine, cable stack or resistance band does not always equal the resistance experienced during the exercise. For these movements, Endura can account for pulley ratios, leverage, body angle, bodyweight distribution, friction or other mechanical factors that materially affect the result.

Strength relationships

Sometimes the most useful measurement is the relationship between two exercises. Endura measures these relationships with standards comparisons, conversions and ratios—each with a specific purpose.

The difference between standards, conversions, comparisons and ratios

The distinction matters.

A conversion should not be presented as a strength ratio. A ratio should not be presented as a population norm. A standards comparison should not claim that two exercises are mechanically equivalent. Endura gives each question its own tool so the result matches the user’s intent.

How an Endura result is calculated

The exact calculation depends on the tool, but the process follows the same structure:

1. Define the performance. Identify the exercise, equipment, resistance, repetitions and any other required test conditions.
2. Normalize the inputs. Convert units and place the performance into the form required by the calculation.
3. Calculate the performance value. This may be an estimated 1RM, total system resistance, effective resistance, repetition score, ratio or another exercise-specific measure.
4. Apply the correct standard or model. Use the exercise-specific thresholds, scaling relationship, conversion model or reference range.
5. Explain the result. Show the user what the result means and, where useful, the key values that produced it.

Every input in an Endura tool serves the calculation, the applicable standard or the result explanation.

Exercise specifications

Strength results are only useful when the exercise being measured is clear. Endura therefore defines the movement and input convention whenever a difference could materially change the result.

Depending on the exercise, the specification can include:

• equipment and resistance source;
• bilateral or unilateral execution;
• the expected range of motion;
• grip or stance;
• assistance or counterweight;
• whether dumbbell resistance means one dumbbell or the combined total;
• whether bodyweight is included in total system resistance;
• machine, lever or cable configuration;
• distance or time for carries and holds; and
• other exercise-specific conditions.

The calculator’s input labels are the final instruction for that tool. If a dumbbell calculator asks for the weight of one dumbbell, enter one dumbbell. If a weighted pull-up tool asks for added resistance, do not add bodyweight again. If a machine tool uses the selected resistance, enter the resistance shown by the machine.

This clarity is a major part of the measurement. Two exercises with similar names are not automatically the same test.

Pounds, kilograms and rounding

Endura supports pounds and kilograms where applicable. Values are normalized before the calculation and converted back to the selected display unit afterward.

Calculations use unrounded internal values whenever possible. Rounding is applied to the displayed result so the output remains practical. Small changes caused only by converting units or rounding a display value do not represent meaningful changes in strength.

We do not add decimal places simply to make a result look more scientific. Loads are shown at a useful training precision. Ratios and scores use additional precision when it helps interpretation.

Estimated one-repetition maximum

An estimated one-repetition maximum, or estimated 1RM, converts a multi-repetition set into a common maximum-strength value. This makes it possible to compare sets completed for different repetition counts without requiring a true maximal attempt.

For sets of 12 repetitions or fewer, Endura calculates both the Epley and Brzycki estimates and uses the lower result. This produces a conservative estimate and avoids selecting the higher formula simply because it returns the larger number.

Epley

Brzycki

Endura rule for 1–12 repetitions

For sets above 12 repetitions, Endura uses a more conservative high-repetition calculation:

Lower-repetition sets generally provide the clearest estimate of maximum strength. As repetitions rise, muscular endurance, pacing and fatigue resistance contribute more to the result. Endura can still calculate the performance, but the interpretation shifts accordingly.

Estimated 1RM is used only when it is appropriate for the exercise. Carries, isometric tests, sled work, explosive movements and some bodyweight or machine exercises require different measures.

How Endura strength standards work

Endura strength standards answer a simple question: How strong is this performance for this exercise?

The answer is built from more than the resistance entered into the calculator. Depending on the exercise, the standard can account for:

• the completed resistance and repetitions;
• estimated maximum strength;
• bodyweight or total system weight;
• age;
• sex-specific reference standards;
• equipment or exercise variation; and
• the way strength scales for that movement.

The result is then compared with exercise-specific thresholds to produce a performance tier, score or supported percentile.

Exercise-specific standards

Each exercise has its own performance profile. The amount of resistance used, the role of bodyweight, the available range of motion, the stability required and the people who commonly perform the exercise all affect the standard.

Endura does not create a new exercise page by changing only the name above a generic chart. Standards are built and checked for the exercise they measure.

Related exercises are reviewed together so the overall system remains coherent, but one exercise is not forced to inherit another exercise’s thresholds when the relationship does not support it.

Bodyweight scaling

Bodyweight is one of the most important—and most frequently mishandled—parts of strength classification.

Heavier athletes generally lift more absolute resistance. Lighter athletes often produce higher simple strength-to-bodyweight ratios. This means that dividing every performance by bodyweight can overcorrect the result, while ignoring bodyweight can make comparisons equally misleading.

Endura uses the scaling method that fits the exercise. Depending on the tool, this can include:

• a direct strength-to-bodyweight ratio;
• bodyweight-specific standards;
• interpolation between bodyweight values;
• an exercise-specific scaling curve; or
• total system resistance for movements in which bodyweight is part of the load.

This is why an Endura result can be more useful than a fixed chart or a single bodyweight multiplier. The method is built around how performance actually changes across body sizes.

Age

Age is used when the tool provides an age-referenced result. The user’s completed performance does not change; the reference used to interpret it does.

An age-adjusted result answers how the performance compares within the relevant age framework. An absolute result answers what was completed regardless of age. Endura keeps those ideas distinct.

Sex-specific standards

When an exercise uses sex-specific reference standards, the selected category determines which thresholds are applied. This reflects the structure of the relevant performance data and produces a more useful comparison than applying one set of thresholds to everyone.

Strength tiers

Endura commonly classifies performance as:

• Beginner
• Novice
• Intermediate
• Advanced
• Elite

These tiers describe the performance—not the person.

They do not prescribe how long someone must have trained. They do not require competition participation. “Elite” identifies the highest performance tier in the standard; it is not automatically a claim about professional or international competitive status.

Tier thresholds are lower-inclusive. If a result equals the Intermediate threshold, it qualifies as Intermediate.

Norms, data and modeling

Endura uses the strongest available combination of exercise-specific data, published evidence, performance records, equipment information and mathematical modeling appropriate to the tool.

Different exercises have different evidence bases. A major competition lift may have extensive public performance records. A machine variation or specialized accessory exercise may require a combination of available performance data, related-exercise relationships and modeling. The method changes because the evidence changes—not because the standard matters less.

We describe methods in three ways:

Observed, hybrid and modeled standards all provide legitimate and useful results. The important questions are whether the method fits the exercise, whether the assumptions are sound and whether the output behaves correctly across the supported range.

What we look for in data

Endura evaluates data and sources for:

• relevance to the exact exercise;
• a clear exercise definition;
• the population represented;
• sample size and coverage;
• measurement quality;
• unit and equipment consistency;
• selection bias; and
• consistency with related evidence.

More data is not automatically better data. A large dataset that mixes different exercises, machines or repetition standards can produce a worse result than a smaller dataset that measures the right performance consistently.

Data quality

Where performance data is used, it is normalized and reviewed before it informs a standard. This includes unit normalization, matching exercise variations, identifying duplicates, reviewing implausible entries, separating assisted and weighted performances, and checking that observations match the tool’s specification.

Exceptional performances are not removed merely because they are exceptional. They are evaluated for validity and relevance like any other observation.

Interpolation and scaling

Not every bodyweight, age or performance value needs a separate observed row. Endura uses interpolation and smooth scaling where appropriate so that results change logically across the supported range.

Interpolation connects supported values. It does not replace the underlying evidence; it makes that evidence usable in a calculator. Every standards model is checked to prevent tier reversals, abrupt jumps and implausible results.

How comparisons, conversions and ratios work

How standards comparisons work

A standards comparison answers: At which exercise am I relatively stronger?

Each performance is evaluated against the standard for its own exercise. Endura then compares the resulting tiers or normalized scores.

This is better than comparing the raw resistance used because different exercises have different mechanics and normal performance levels. A 200-pound result in one movement cannot be assumed to equal a 200-pound result in another.

If a user scores higher in exercise A, it means the performance ranks higher against exercise A’s standard. It does not mean exercise A and exercise B use equivalent resistance, and it does not predict the exact result of a conversion.

Standards comparisons are useful for identifying relative strengths, seeing where development differs and choosing what to test or train next.

How exercise conversions work

An exercise conversion answers: What performance in exercise B is approximately equivalent to this known performance in exercise A?

Endura first places the known performance into the form required by the conversion. This may involve unit normalization, estimated 1RM or another common measure. It then applies the relationship built for that specific exercise pair and returns the estimated equivalent load, repetitions or performance range.

The relationship can be based on:

• paired performance data;
• published research;
• related exercise datasets;
• known equipment or leverage differences;
• biomechanical similarity; and
• exercise-specific modeling.

Conversions are specific to the exercise pair. Endura does not use one universal percentage for every “similar” movement.

Individual results can vary because people train exercises differently and have different leverages, technique, range of motion and muscle-group strengths. Where that variation is meaningful, the tool can show a useful range in addition to the central estimate.

One calculator can support both directions when the relationship can be applied responsibly in reverse. Reverse wording does not need a separate page or a separate model simply because the user searches the exercises in the opposite order.

How strength ratios work

A strength ratio answers: What is the relationship between these two known performances?

The basic calculation is:

The tool defines which exercise is the numerator, which is the denominator and whether the comparison uses entered resistance, estimated 1RM, total system resistance or another appropriate measure.

Reference ranges can represent a commonly observed relationship, a balanced-development benchmark, a sport-specific target or a modeled relationship. Endura identifies which interpretation applies.

A ratio outside the reference range is information—not a diagnosis. It may reflect training specialization, technique, exercise familiarity, anatomy, equipment or a meaningful difference in development.

Most importantly, a ratio is not a conversion. A ratio measures two known performances. A conversion estimates one unknown performance. Endura provides separate tools because users are asking separate questions.

How effective resistance is calculated

Displayed resistance and effective resistance are not always the same.

During a push-up, only part of bodyweight is supported by the hands. During an incline or decline variation, that percentage changes. A cable machine can divide the selected resistance through its pulley system. A landmine changes leverage as the angle changes. A sled’s resistance depends on friction and the surface, not simply the weight placed on it.

Effective-resistance tools account for the variables that matter to the movement, which can include:

• bodyweight distribution;
• body angle and geometry;
• support and contact points;
• lever length;
• pulley ratio;
• machine leverage;
• band elongation;
• sled friction and surface; and
• landmine angle.

The result describes the resistance estimated by the tool’s mechanical model. The tool specification explains the setup and assumptions so users can enter the performance correctly and compare it consistently.

What appears on each tool page

This methodology page explains the system shared across Endura. Each calculator provides the details required to understand that specific tool.

Tool specifications

The specifications include:

• what the tool measures;
• the exercise or test definition;
• required inputs;
• the weight-entry convention;
• the supported input range;
• the primary calculation;
• the result produced; and
• the review date and methodology version.

Norm and model information

When relevant, the page identifies:

• the reference population or performance framework;
• whether the standard is observed, hybrid or modeled;
• how bodyweight is handled;
• how age is handled;
• whether sex-specific standards are used;
• the important sources;
• key exercise-specific assumptions; and
• the most useful interpretation of the result.

How your result was calculated

The results screen shows the important path from the user’s performance to the final result. Depending on the tool, this can include:

• entered resistance and repetitions;
• estimated 1RM;
• strength-to-bodyweight ratio;
• total system or effective resistance;
• the applicable standard or reference range;
• the final tier or score; and
• links to the most relevant next tools.

For example:

The explanation should be specific to the result—not a generic paragraph repeated beneath every calculator.

Quality control and appropriate use

Quality control

Before an Endura tool is published, it is checked for:

1. the correct exercise definition;
2. clear input instructions;
3. unit conversion;
4. calculation accuracy;
5. correct tier-boundary behavior;
6. realistic low, middle and high results;
7. consistency with related exercises;
8. usable results and interpretation; and
9. mobile and desktop calculator behavior.

The standards system is also checked as a whole. Related exercises should make sense together, but they should not be artificially identical. Scaling should be smooth without flattening meaningful differences. Results should remain useful across the supported range instead of working only for an average-sized user.

Accuracy and appropriate use

Endura is designed to give users a strong, practical measurement of their performance using the information available outside a laboratory.

For the best result:

• perform the exercise as specified;
• enter the resistance exactly as requested;
• use a complete and consistent range of motion;
• compare performances completed under similar conditions; and
• use lower-repetition sets when maximum-strength estimation is the goal.

Normal differences in technique, equipment and day-to-day readiness can affect any strength test. Those differences do not make the standard invalid; they are reasons to test consistently.

Endura tools are built for strength measurement, comparison, goal setting and training decisions. They are not a substitute for medical diagnosis, injury evaluation or return-to-play assessment.

How Endura improves its methods

Endura’s standards and tools are living measurement systems. They are reviewed and improved as better data, stronger evidence and more complete exercise-specific information become available.

A method may be updated when we identify:

• better exercise-specific data;
• improved scaling;
• a stronger conversion relationship;
• an equipment-specific difference;
• a calculation or unit issue;
• a clearer exercise specification;
• a better way to explain the result; or
• an opportunity to make related tools more consistent.

Material changes that affect calculations, classifications or interpretation are recorded in the methodology version history. This makes improvement visible rather than silently changing what a result means.

Evidence, sources and version history

Endura connects each source to the calculation, norm or model it supports. Tool pages identify the evidence most relevant to that exact exercise; this page lists the foundational methods used across Endura.

Foundational references

1. Brzycki (1993): Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue.
2. LeSuer et al. (1997): The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift.
3. Nuzzo et al. (2024): Maximal Number of Repetitions at Percentages of the One Repetition Maximum.
4. Jaric (2002): Muscle Strength Testing: Use of Normalisation for Body Size.
5. Allometric Scaling of Strength Measurements to Body Size (2009).
6. van den Hoek et al. (2024): Normative Data for the Squat, Bench Press and Deadlift Exercises in Powerlifting.

How sources are used

These references do not create one universal strength standard. They support specific parts of the measurement system: estimated-max calculations, repetition relationships, body-size scaling and population norms.

Exercise-specific standards and conversion models can also use published research, documented performance records, equipment specifications and defined exercise-specific modeling. A source is used only when its exercise, population and test conditions fit the result it is being used to support. The applicable tool page identifies the method and the most important sources for that tool.

Methodology version history

Frequently asked questions