Mesolab › Tools › One rep max calculator
One rep max (1RM) calculator
Enter the weight and reps of one hard set to estimate your one rep max. If you stopped before failure, add the reps you had left in reserve. Below the result: the weight for every percentage of your 1RM and for every rep count.
Keep your 1RM up to date without testing it
Mesolab estimates your 1RM from the sets you log with this same formula and suggests a weight for every set, aimed at that set's target reps in reserve. Free to download; your first completed workout is free.
1RM percentage chart
The weight at each percentage of your one rep max, from an estimated 1RM of 262.5 lb, rounded to the nearest 2.5. Max reps is how many reps that weight allows to failure by the same formula; past 20 reps every formula drifts, so the chart shows 20+.
| % of 1RM | Weight | Max reps |
|---|---|---|
| 100% | 262.5 lb | 1 |
| 95% | 250 lb | 1 |
| 90% | 237.5 lb | 3 |
| 85% | 222.5 lb | 5 |
| 80% | 210 lb | 7 |
| 75% | 197.5 lb | 10 |
| 70% | 185 lb | 12 |
| 65% | 170 lb | 16 |
| 60% | 157.5 lb | 20 |
| 55% | 145 lb | 20+ |
| 50% | 132.5 lb | 20+ |
Rep max chart: weight for 1 to 20 reps
The heaviest weight for each rep count, from an estimated 1RM of 262.5 lb: taken to failure, and with 2 reps left in reserve, a common target for muscle-building sets.
| Reps | % 1RM | To failure | At 2 RIR |
|---|---|---|---|
| 1 | 100% | 262.5 lb | 237.5 lb |
| 2 | 94% | 245 lb | 232.5 lb |
| 3 | 91% | 237.5 lb | 225 lb |
| 4 | 88% | 232.5 lb | 220 lb |
| 5 | 86% | 225 lb | 212.5 lb |
| 6 | 83% | 220 lb | 207.5 lb |
| 7 | 81% | 212.5 lb | 202.5 lb |
| 8 | 79% | 207.5 lb | 197.5 lb |
| 9 | 77% | 202.5 lb | 192.5 lb |
| 10 | 75% | 197.5 lb | 187.5 lb |
| 12 | 71% | 187.5 lb | 180 lb |
| 15 | 67% | 175 lb | 167.5 lb |
| 20 | 60% | 157.5 lb | 152.5 lb |
Which 1RM formula this calculator uses
The Epley formula, counting the reps you had left in reserve as reps you could have done:
Estimated 1RM = weight × (1 + (reps + RIR) ÷ 30)
A single at 0 RIR is your 1RM as it is. For a set to failure, leave RIR at 0 and the formula is plain Epley.
Worked through: 225 lb for 5 reps to failure gives 225 × (1 + 5 ÷ 30) = 262.5 lb. The same 225 lb for 5 with 2 reps left counts as 7 reps: 225 × (1 + 7 ÷ 30) = 277.5 lb. The charts run the formula backwards: 75% of 262.5 lb is 196.9 lb, shown as 197.5 lb, and 1 ÷ 0.75 = 1 + 10 ÷ 30, so that weight allows about 10 reps.
It is the same formula Mesolab uses to estimate a 1RM from the sets you log, and the same one behind the RIR calculator and Lift Forecast. The three can still show slightly different numbers because they round differently.
An estimate, not a test. Every rep-based formula is an approximation. It is closest from a hard set of about 3 to 10 reps, less reliable past 12 to 15, and only as good as the reps in reserve you enter: newer lifters often have more left than they think, which makes the estimate read low.
Common questions
How do I calculate my one rep max without maxing out?
Take a weight you can lift for 3 to 10 good reps, do as many as you can with clean form, and enter the weight and reps above. If you stopped with reps left, enter how many: the calculator counts them.
What percentage of my 1RM should I train at?
For building muscle, most working sets land between about 65% and 85% of 1RM, which is 5 to 15 reps taken close to failure. Heavier work above 85% is mostly for practising maximal strength.
How many reps can I do at 80% of my 1RM?
About 7 to failure by the Epley formula, or 5 if you leave 2 in reserve. At 70% it is about 12, at 90% about 3. Real numbers vary by lifter and lift: they tend to run higher on machines and leg exercises than on the bench press.
Epley or Brzycki: which 1RM formula is better?
They agree closely at low reps and drift apart as reps rise. Brzycki gives a higher estimate for sets above 10 reps and stops working near 37 reps; Epley stays sensible across the 8 to 20 rep range most training happens in, which is why Mesolab uses it.
Should I test my 1RM or estimate it?
For choosing training weights, an estimate from a hard set is usually enough and costs far less recovery than a max attempt. If you compete, test the lift itself.