How accurate is a 1RM calculator?
Within a few percent, if the input set was genuinely hard: 2 to 6 reps taken close to failure. Easy sets understate your max by exactly as much as they were easy, which is why this calculator lets you enter RPE.
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POWERLIFTING CALCULATOR
1RM CALCULATOR
Estimate your one rep max from any working set. Add RPE if you left reps in the tank, then get your full percentage chart and rep maxes.
UNITS
SQ SQUAT
ESTIMATED 1RM
— LB
BP BENCH
ESTIMATED 1RM
— LB
DL DEADLIFT
ESTIMATED 1RM
— LB
RPE is optional. Leave it blank for a set taken to failure. Any lift works in any slot.
ESTIMATED TOTAL
0
LB
CHART FOR
Percentage chart
| % of 1RM | Weight |
|---|
Rep maxes
| Reps | Weight |
|---|
The method
How the estimate works
A one rep max is the heaviest weight you can lift for one clean rep. Testing it directly is slow, because every near-max attempt needs full recovery, and past 40 it is often not worth the injury risk.
So this page estimates it from a set you already did. The main number uses the Epley formula, the most common estimator in powerlifting programming:
1RM = WEIGHT × (1 + REPS ÷ 30)
For the tightest estimate, log a hard set of 2 to 6 reps taken close to failure. That set is already near a max effort, so the formula has little to guess. Past about 10 reps the number goes loose, because the set is testing endurance more than maximal strength.
Under each result you will also see the Brzycki estimate. More on why below.
Reps in reserve
Why this calculator asks for RPE
Most 1RM calculators assume every set went to failure. Yours probably did not. A set of 5 that had two more reps in it is not a 5-rep max, and plugging it in as one underestimates you.
RPE fixes that. On the reps-in-reserve scale used in powerlifting, RPE 10 means nothing left, RPE 9 means one rep left, RPE 8 means two [1]. The calculator adds the reps you left back before it runs the formula, so 5 reps at RPE 8 is treated like a 7-rep max. Lifters rate this scale reasonably well, and they get better at it with practice [1][2].
New to RPE? Start with RPE for powerlifting, then come back.
| Reps | RPE 10 | RPE 9 | RPE 8 | RPE 7 |
|---|---|---|---|---|
| 1 | 100% | 94% | 91% | 88% |
| 2 | 94% | 91% | 88% | 86% |
| 3 | 91% | 88% | 86% | 83% |
| 4 | 88% | 86% | 83% | 81% |
| 5 | 86% | 83% | 81% | 79% |
| 6 | 83% | 81% | 79% | 77% |
Read it as "% of 1RM." Three reps at RPE 8 sits around 86%. These values come straight from the Epley formula, so treat them as a starting point, not a law. Your own chart will drift a few points depending on the lift and how you are built.
1RM chart
Reps to percentage of 1RM
How much of your max each rep count uses, for a set taken to failure:
| Reps to failure | % of 1RM |
|---|---|
| 1 rep | 100% |
| 2 reps | 94% |
| 3 reps | 91% |
| 4 reps | 88% |
| 5 reps | 86% |
| 6 reps | 83% |
| 7 reps | 81% |
| 8 reps | 79% |
| 9 reps | 77% |
| 10 reps | 75% |
| 12 reps | 71% |
Converting a 3RM or 5RM: multiply the weight by (1 + reps ÷ 30). A 3RM of 275 lb is about a 303 lb max. A 5RM of 225 lb is about 263 lb. Going the other way, divide your max by the same number to find a rep target: a 315 lb squatter should expect around 270 lb for 5.
Formulas
Epley vs Brzycki
| Formula | Equation | Behavior |
|---|---|---|
| Epley | w × (1 + r/30) | The powerlifting default. Slightly more generous from low-rep sets. |
| Brzycki | w × 36 / (37 − r) | About 4% lower from a 3 to 5 rep set. Meets Epley at 10 reps. |
Neither is "right." They bracket the answer. If you are coming back from a layoff or a bad week, program off the lower number. If the input set was a clean, honest top set, Epley is fine.
Training zones
What to do with your numbers
Your estimated max anchors every working weight. Run your sets inside the zone that matches your goal:
| % of 1RM | Zone | What to run |
|---|---|---|
| 90–95% | Peaking | Singles & doubles for meet prep |
| 80–90% | Heavy strength | Sets of 2–5 |
| 70–80% | Strength volume | Sets of 4–8 |
| 60–70% | Hypertrophy | Sets of 6–10 |
| 50–60% | Warm-up & technique | Fast, clean reps |
Most of your training should live in the 70 to 85% band. That is where strength gets built without the recovery bill of constant heavy singles. Why you don't max out all the time covers the reasoning.
Garbage in, garbage out
How to get an honest estimate
- Use a top set, not a back-off set. The first hard set after warm-ups, not set five of the day.
- Hold meet standards. Depth on the squat, a pause on the bench, a full lockout on the pull. A high squat inflates the number and the program built on it.
- Rate RPE right after the set, before the story you tell yourself gets better.
- Recalculate every 3 to 4 weeks, or whenever a top set moves clearly faster than it should.
- Save the true max for the platform. Peaking is its own skill. The meet prep guide walks through it.
Lifting after 40? Estimating instead of testing matters even more, because recovery is the constraint, not strength. How to powerlift after 40 lays out the whole approach.
Stop guessing your intensity
A 1RM is only useful if your programming actually uses it. Every Center Mass Strength track is built off your maxes. The app logs weight, reps and RPE, sets every working weight for you, and moves your training max as you get stronger.
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FAQ
Questions lifters ask
What rep range gives the best 1RM estimate?
Two to six reps taken close to failure. That set is close enough to a true max effort that the formula has little to extrapolate. Past about 10 reps the estimate drifts, because you are testing endurance more than maximal strength.
How do I convert a 3RM or 5RM to a 1RM?
Multiply the weight by (1 + reps / 30). A 3RM of 275 lb works out to about 303 lb. A 5RM of 225 lb works out to about 263 lb. Or enter the set above and the calculator does it for you.
How does RPE change the 1RM estimate?
RPE tells the calculator how many reps you left in the tank. RPE 10 means none, RPE 9 means one, RPE 8 means two. The calculator adds those reps back before running the formula, so 5 reps at RPE 8 is treated like a 7-rep max.
What percentage of my 1RM is 5 reps?
About 86% by the Epley formula, if the set is taken to failure. At RPE 8, 5 reps lands closer to 81%.
Should I test my true 1RM instead of estimating it?
For programming, no. An estimate drives training percentages just fine, and you skip the fatigue and injury risk of maxing out. Save true maxes for the platform.
Which formula does this 1RM calculator use?
Epley, 1RM = weight x (1 + reps / 30), as the main number, with Brzycki, 1RM = weight x 36 / (37 - reps), shown alongside. Brzycki reads a few percent lower from low-rep sets, and the two meet at 10 reps.
Sources
References
- Zourdos MC, Klemp A, Dolan C, et al. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res. 2016;30(1):267-275. PubMed
- Helms ER, Cronin J, Storey A, Zourdos MC. Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength Cond J. 2016;38(4):42-49. PubMed