One Rep Max Calculator
Estimate your 1RM and a percentage training table.
The number of clean reps you finished at this weight.
Estimated 1RM (Epley)
- Epley estimate
- 116.7 kg
- Brzycki estimate
- 112.5 kg
- 95%
- 110.8 kg
- 90%
- 105 kg
- 85%
- 99.2 kg
- 80%
- 93.3 kg
- 75%
- 87.5 kg
- 70%
- 81.7 kg
- 65%
- 75.8 kg
- 60%
- 70 kg
Estimates only. Never attempt a true one-rep max without a spotter and a proper warm-up. Accuracy is best in the 1 to 10 rep range.
How the one-rep max calculator works
Your one-rep max (1RM) is the most weight you can move for a single repetition. It is the yardstick strength programmes use to set working loads, but testing it directly is tiring and risky. This tool estimates it from a set you have already completed, using two established formulas.
You enter the weight you lifted and the number of reps you finished, and the calculator returns both estimates:
- Epley:
1RM = weight * (1 + reps / 30) - Brzycki:
1RM = weight * 36 / (37 - reps)
Both take a sub-maximal set and project what a single all-out rep would have been. They agree closely at low reps and spread apart as reps rise, so the estimate is most trustworthy when you base it on a heavy set of a few reps rather than a light set of many. Reps are capped at twelve for that reason, and because the Brzycki formula breaks down as its denominator shrinks toward zero near 37 reps.
The 1RM is linear in the load, so the result comes out in whatever unit you enter. Choosing kilograms or pounds only changes the label, never the number.
Worked example
Suppose you squat 100 for 5 reps.
- Epley:
100 * (1 + 5 / 30) = 100 * 1.1667 = 116.67 - Brzycki:
100 * 36 / (37 - 5) = 3600 / 32 = 112.50
So your estimated max is roughly 113 to 117, a useful working range rather than a single exact figure.
The calculator then turns the Epley estimate into a table of training loads at common intensities:
| Intensity | Load |
|---|---|
| 95% | 110.83 |
| 90% | 105.00 |
| 85% | 99.17 |
| 80% | 93.33 |
| 75% | 87.50 |
| 70% | 81.67 |
| 65% | 75.83 |
| 60% | 70.00 |
Each load is that percentage of 116.67. So if your programme calls for a set at 80 percent, you would load around 93 on the bar.
How to use it
- Choose your unit to match your plates, kilograms or pounds.
- Enter the weight you lifted on a recent working set.
- Pick the reps you completed cleanly at that weight, from one to twelve.
- Read your two 1RM estimates, then use the percentage table to set loads for your next session.
Limitations
These are estimates, not a measured maximum. They assume the reps were honest, completed with full range and good form to near failure; padding the rep count inflates the result. The formulas were fitted to typical trainees and may not match your individual strength curve, and they are least accurate on high-rep sets. Use the figures to plan loads and track progress over time, build up gradually, and never attempt a genuine one-rep max without a thorough warm-up and a spotter.
Frequently asked questions
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can lift for a single clean repetition of an exercise. It is the standard reference point for strength training because most programmes prescribe loads as a percentage of it, for example five sets of three reps at 85 percent. Testing a true 1RM is taxing and carries some injury risk, so this calculator estimates it from a set you have already done instead.
How does the calculator estimate my 1RM without a max attempt?
It uses two well known formulas that infer a single-rep maximum from a sub-maximal set. Enter the weight you lifted and how many reps you managed, and it returns both estimates. The fewer reps you used, the closer the estimate is to the truth, which is why the input is capped at twelve reps. A heavy triple gives a far better estimate than a light set of twenty.
Why do the Epley and Brzycki numbers differ?
They are two different curve fits to the same idea, so they agree closely at low reps and drift apart as reps climb. Epley tends to read slightly higher at moderate reps, Brzycki slightly lower. Neither is the single correct answer; treat the pair as a sensible range rather than a precise figure, and use whichever has matched your own lifts in the past.
What are the percentage loads for?
Once you have a 1RM, training programmes express working sets as a share of it. The table converts your estimated max into the loads at common intensities from 95 percent down to 60 percent, so you can pick a weight straight away. As a rough guide, sets near 90 percent build maximal strength, the 70 to 80 percent band suits hypertrophy, and lighter loads suit speed and technique work.
Does the unit I choose change the result?
No. The 1RM scales directly with the weight you enter, so the estimate comes out in the same unit you put in. Pick kilograms or pounds to match how your plates are labelled, and every figure, including the percentage table, is shown in that unit. Switching units only changes the label, never the underlying maths.