One-rep max (1RM) calculator
Enter a weight and how many reps you did with it — get your estimated one-rep max (1RM) and working weights from 50 to 100 %. No heavy single needed.
Percentages of 1RM
| % of 1RM | Weight | ≈ Reps |
|---|---|---|
| 100% | 116.7 kg | 1 |
| 95% | 110 kg | 2 |
| 90% | 105 kg | 3 |
| 85% | 100 kg | 5 |
| 80% | 92.5 kg | 8 |
| 75% | 87.5 kg | 10 |
| 70% | 82.5 kg | 12+ |
| 65% | 75 kg | 12+ |
| 60% | 70 kg | 12+ |
| 55% | 65 kg | 12+ |
| 50% | 57.5 kg | 12+ |
What to load for N reps
| Reps | Weight |
|---|---|
| 1 | 117.5 kg |
| 2 | 110 kg |
| 3 | 105 kg |
| 5 | 100 kg |
| 8 | 92.5 kg |
| 10 | 87.5 kg |
| 12 | 82.5 kg |
Weights are rounded to a plate step: 2.5 kg or 5 lb.
Other formulas
| Formula | 1RM |
|---|---|
| Epley in the app | 116.7 kg |
| Brzycki | 112.5 kg |
| Lombardi | 117.5 kg |
| Mayhew | 119 kg |
| O'Conner | 112.5 kg |
| Wathan | 116.6 kg |
| Lander | 113.7 kg |
How to estimate your 1RM
- 1
Take a working set
Best is a heavy set of 3–8 reps done with clean form, short of form failure.
- 2
Enter weight and reps
You get the 1RM estimate by the Epley formula and by five others right away.
- 3
Plan by percentages
The table shows working weights: 75–85 % of 1RM, for example, is a typical strength zone for 5–8 reps.
What a 1RM is and why it matters
Your 1RM, or one-rep max, is the weight you can lift exactly once with good form. Programs use it to set loads (“3x5 at 80 %”), and it's the cleanest way to compare strength between sessions.
Testing a true max is risky and draining, so it's estimated from a regular set. The Epley formula: 1RM = weight × (1 + reps / 30). For example, 100 kg × 5 reps ≈ 116.7 kg. The fewer reps in the set, the closer the estimate; past 10–12 reps the formulas drift apart.
The formulas agree at 3–6 reps and diverge at higher reps. Rather than hunting for the “most accurate”, stick to one — then a rising estimate really means rising strength.
Track your 1RM automatically
LiftChat estimates your 1RM from every set — with a chart per lift, personal records and a hint on how much to add next time.
A new account gets 14 days of Standard right away: every feature, with half the assistant limit. No card and no auto-charge — after that you stay on the free plan, where workout logging has no limits.
How it works →Questions
Which 1RM formula is the most accurate?
There's no single one: Epley and Brzycki are the most common and agree closely at 2–10 reps. What matters is using one formula consistently to see the trend. LiftChat uses Epley.
How many reps should I enter?
From 1 to 12. The estimate is closest from a set of 3–8 reps; sets over 12 reps are counted as 12.
Why is my 1RM equal to the weight at 1 rep?
Because a single is the max. Epley taken literally would add 3 % — a quirk of the formula, removed in the app.
How often should I recalculate my 1RM?
After every heavy set — which is what LiftChat does: the estimate updates every workout and the chart shows the trend.
Can I plan training with my 1RM?
Yes: take the percentage for your goal from the table — say, 70–80 % for 8–10 reps for size, or 85–90 % for 3–5 reps for strength.