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e1RM calculator — your estimated 1RM.
The e1RM calculator estimates your one rep max from a submaximal set, so you never have to grind a true single. Enter a weight and reps for a formula-based estimate, or add an RPE rating to use the Zourdos RPE chart for a sharper, auto-regulated number. It updates instantly, no signup.
Your percentage training table
The weight to load at each % of your estimated max, with an approximate rep range to program from.
RPE to % of 1RM.
The Zourdos / RTS chart the RPE mode uses: the percentage of your 1RM that a set represents, by reps and RPE. Read down a rep column, across from your RPE.
| RPE | 1 rep | 2 reps | 3 reps | 4 reps | 5 reps | 6 reps |
|---|---|---|---|---|---|---|
| 10 | 100% | 95.5% | 92.2% | 89.2% | 86.3% | 83.7% |
| 9.5 | 97.8% | 93.9% | 90.7% | 87.8% | 85% | 82.4% |
| 9 | 95.5% | 92.2% | 89.2% | 86.3% | 83.7% | 81.1% |
| 8.5 | 93.9% | 90.7% | 87.8% | 85% | 82.4% | 79.9% |
| 8 | 92.2% | 89.2% | 86.3% | 83.7% | 81.1% | 78.6% |
| 7.5 | 90.7% | 87.8% | 85% | 82.4% | 79.9% | 77.4% |
| 7 | 89.2% | 86.3% | 83.7% | 81.1% | 78.6% | 76.2% |
| 6.5 | 87.8% | 85% | 82.4% | 79.9% | 77.4% | 75.1% |
Chart values from the Reactive Training Systems / Zourdos RPE model, validated in Zourdos et al. (2016). RPE is reps in reserve inverted — RPE 8 means about 2 reps left in the tank, RPE 10 means none.
Two ways to estimate.
No black box. Without RPE the tool averages two validated formulas; with RPE it uses the Zourdos chart for an auto-regulated estimate.
1RM = W × (1 + R ÷ 30) Averaged with Brzycki W×36/(37−R). 100 kg × 5 → 115 kg.
e1RM = W ÷ (% ÷ 100) Look up % for reps + RPE, then scale up. 100 kg × 5 @ RPE 8 = 81% → 123 kg.
RIR = 10 − RPE RPE 8 leaves 2 reps in reserve — the chart accounts for those.
The RPE method is sharpest for trained lifters who rate exertion reliably, at 1 to 6 reps. The formula method is best for 1 to 10 reps. Sources: Epley and Brzycki relationships; the Reactive Training Systems / Zourdos RPE chart, Zourdos et al. (2016).
Related strength calculators.
Same math, dialled in per lift and per goal — plus the tracker that puts your numbers to work.
e1RM questions.
What is e1RM?
e1RM stands for estimated one rep max — the heaviest single you could likely lift, calculated from a submaximal set rather than an actual max attempt. It is estimated either from the reps you did, using the Epley and Brzycki formulas, or from reps plus an RPE rating using the Zourdos RPE chart.
How do you calculate e1RM from RPE?
To calculate e1RM from RPE, look up the percentage of 1RM that matches the reps and RPE of your set on the Zourdos RPE chart, then divide the weight by that percentage. For example, 100 kg for 5 reps at RPE 8 maps to 81 percent, giving an e1RM of about 123 kg.
What is the difference between 1RM and e1RM?
A 1RM is a tested one rep max — the actual heaviest single you lifted on the day. An e1RM is an estimate of that number derived from a lighter set, so you never have to grind a true max. e1RM is safer, repeatable every session, and the basis of most auto-regulated programming.
Is RPE-based e1RM more accurate?
For a trained lifter who rates RPE reliably, the RPE-based e1RM is usually sharper than reps alone, because RPE captures how close the set was to failure. A set of 5 taken to RPE 8 leaves reps in reserve, and the chart accounts for that instead of assuming the set was maximal.
Is this e1RM calculator free?
Yes, completely free with no signup. Save your e1RM to your Nishaana account and it auto-applies to your next workout, tracking your estimated max over time so you can see strength trend up without ever testing a true single.
Save your e1RM. Track it.
Free in your browser — Nishaana tracks your estimated max over time and auto-applies it to every workout, so strength trends up without max testing.
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