Hack Squat 1RM Calculator

Read the hack-squat target on your machine

Use the estimate on the same hack-squat machine and keep the plates-only or starting-weight-included convention unchanged. Record the machine and setup before comparing workouts.

Choose how you count hack-squat weight

Enter a hard set from the same hack-squat machine, stance, depth, and seat setup. Choose whether the recorded weight is plates only or includes a known starting weight, and keep the machine label, unit, and setup notes with the entry.

Use the convention displayed by your machine rather than guessing an empty sled value. The estimate is for that hack-squat setup; it does not apply a back-squat conversion or silently add machine resistance.

Weight unit

Choose the unit shown on your weights.

Weight lifted

Enter the weight used for your completed set, following the weight convention below.

Repetitions completed

Enter 1–10 full repetitions from a hard set with consistent technique.

Repetitions to estimate

Choose how many repetitions you want to estimate a weight for, from 1 to 10.

Percentage of your estimated max

Enter the percentage weight you want to calculate.

Available weight increase

Leave blank for the exact estimate, or enter the smallest total weight increase your equipment allows.

How are you counting the weight?

Choose the description that matches the number you entered. Keep this choice the same when comparing results.

Machine name

Optionally name the exact machine so you can compare like-for-like next time.

Setup notes

Record the seat, grip or stance you want to repeat next time.

Compare rep targets on the same hack squat

Each point is a different estimated rep target on the same machine. It is not a comparison between hack-squat designs, leg press and barbell squat.

The example below shows how to read the graph. Your graph updates after you calculate, and the complete values remain available in the table beneath it.

Follow a machine hack-squat example

The result uses only the values you enter and the method shown below. Rounded workout values stay separate from the underlying calculation.

A checked machine hack squat example

This checked example uses pounds. It comes directly from the same calculator that produces your result.

Select “Use example” to load these values. If you choose kilograms in the calculator, the chart and personalized tables recalculate in kilograms.

Understand the limits of the machine estimate

Use this as a repeatable estimate, not proof of your true one-rep max. The available study used to check the Brzycki equation tested free-weight bench press in 103 college women. That study checks the equation in that setting; It did not test machine hack squat. Hack-squat machines can differ in sled angle, leverage and starting resistance, so compare results only on the same machine and setup. Use a hard set of 1–10 full repetitions. Stopping early can understate the estimate, and this calculator does not accept higher-repetition sets.

• Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue — Matt Brzycki (1993).
• Accuracy of Prediction Equations for Determining One Repetition Maximum Bench Press in Women Before and After Resistance Training — Mayhew et al. (2008).
• Guide for the Use of the International System of Units (SI) — NIST (2008).

Choose another hack-squat task

• Machine Hack Squat Live Endura

  Explore hack-squat standards while retaining the machine convention.

• RPE Calculator

  Record effort for the completed hack-squat set.

• Warm-Up Set Calculator

  Calculate chosen warm-up percentages on the same machine.

• Leg Press 1RM Calculator

  Keep a leg-press estimate as a separate exercise and machine record.

• Leg Extension 1RM Calculator

  Track leg-extension performance from its own completed set.