One Rep Max Calculator
Estimate how much weight you may be able to lift for one rep, then turn that estimate into weights for your next workout. Enter the weight and clean reps from one hard set—no all-out max attempt required.
Your results show estimated weights for sets of 1–12 reps, weights at 50–95% of your estimated max, and two ways to progress next time: lift more weight for the same reps or do one more rep at the same weight. Choose a rounding option so the targets match the plates or dumbbells available at your gym.
Name the exercise and save the result to your Endura dashboard. The next time you calculate that lift, you can compare the new result with your earlier results. You can also copy, share, or print it for your next workout.
What Your Estimated One Rep Max Means
Your estimated one-rep max is the weight this calculator predicts you could lift once for the same exercise, setup and technique. It comes from the set you entered; it is not a single you have already lifted.
Example: 225 lb for 5 reps gives an estimated 1RM of 263 lb. That is about 38 lb more than the weight used for the set.
Single you completed
250 lb × 1 → 250 lb
This is a lift you actually did. It does not prove it was your heaviest possible single.
Max estimated from reps
225 lb × 5 → 263 lb
This is a prediction from a hard set. You have not lifted the projected single yet.
Use the estimate to compare hard sets from the same lift when the rep counts differ. A higher estimate suggests progress only when the exercise, setup, technique and effort are similar.
Rep Max Chart: Choose Your Next Set Weight
From the 225 lb × 5 example, the chart shows about 240 lb for three reps and 205 lb for eight, rounded to the nearest 5 lb. The completed set is marked so you can see where every estimate starts.
As the rep target rises, the estimated weight falls. Weights for two or more reps are rounded to the nearest 5 lb. Your completed set is highlighted.
| Rep target | Estimated weight |
|---|---|
| 1 rep | 263 lb |
| 2 reps | 245 lb |
| 3 reps | 240 lb |
| 4 reps | 230 lb |
| 5 reps — your set | 225 lb |
| 6 reps | 220 lb |
| 7 reps | 215 lb |
| 8 reps | 205 lb |
| 9 reps | 200 lb |
| 10 reps | 195 lb |
| 11 reps | 190 lb |
| 12 reps | 190 lb |
| What you want to do | Example weight |
|---|---|
| A heavier set of 3 reps | About 240 lb |
| Another set of 5 reps | About 225 lb |
| A longer set of 8 reps | About 205 lb |
In this example, five reps at 225 lb is about 86% of the unrounded estimate. That percentage describes this formula and example; it is not a promise that every lifter can complete five reps at 86%.
What to Try in Your Next Workout
Choose one option in the result card: add a little weight for the same reps, or keep the weight and aim for one more clean rep. These are practical targets for the same exercise and setup, not guaranteed performances.
Use a 1RM Percentage From Your Program
If your program calls for 80% of your 1RM, the 225 lb × 5 example gives about 210 lb after rounding to the nearest 5 lb. The table shows 50–95% of the same estimate.
| Percent of estimated 1RM | Example weight |
|---|---|
| 50% | 130 lb |
| 60% | 160 lb |
| 65% | 170 lb |
| 70% | 185 lb |
| 75% | 195 lb |
| 80% | 210 lb |
| 85% | 225 lb |
| 90% | 235 lb |
| 95% | 250 lb |
The estimated 1RM itself is the 100% reference. Completed a single? Enter its weight and 1 rep to use that lifted weight as the reference. Otherwise, use the percentage your program gives you. If your program uses a separate training max, calculate from that value instead. A percentage plans weight; it does not promise how many reps you will complete.
Save and Track Your One Rep Max
Name the exercise before you save so your dashboard can keep that lift’s results together. When you calculate it again, compare the new estimate with earlier hard sets from the same exercise.
| Completed set | Estimated 1RM |
|---|---|
| 225 lb × 5 reps | 263 lb |
| 230 lb × 5 reps | 268 lb |
In this example, 225 lb for five reps and 230 lb for five reps produce different estimates. Treat the difference as progress only when both sets used the same setup and a similar level of effort.
How Accurate Is Your Estimated 1RM?
Use a recent set with clean technique and a hard final rep. The calculator knows the weight and reps you enter, but it cannot know how many more reps you could have completed.
- Enter only reps you completed with the form and range of motion you want to repeat.
- Count weight the same way every time, including the bar when you use one.
- Keep the exercise, equipment and setup consistent when you compare results.
A lower-rep hard set requires less prediction than a long set. A set stopped with several reps left can underestimate your max. No formula can calculate a reliable personal error range from weight and reps alone.
How to Calculate One Rep Max From Reps
For sets of two or more reps, the calculator uses the Epley equation: estimated 1RM = weight × (1 + reps ÷ 30). If you enter one rep, the result is the weight you actually lifted rather than a prediction of something heavier.
For the example set, 225 lb × (1 + 5 ÷ 30) = 262.5 lb, displayed as 263 lb. An eight-rep target works backward from that estimate and rounds to 205 lb on the nearest 5 lb grid.
The formula cannot see fatigue, technique, exercise differences or how close the set was to failure. Research on bench-press prediction found that accuracy changed with the number of reps in the tested sample, so the result should guide planning rather than guarantee a lift.