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Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. It’s the reference point strength programs are built on — most prescribe weights as a percentage of it — but actually testing a true 1RM is risky and tiring. Instead you estimate it from a weight you lifted for a few reps.
Enter a weight and the number of clean reps you managed, and this tool estimates your 1RM (Epley formula, with Brzycki as a cross-check) plus the weights to use for 2–12 reps.
One-Rep Max Calculator: step-by-step worked example
- Weight lifted
- 225
- Repetitions
- 5
- 1
Rep multiplier
Multiplier = 1 + Reps ÷ 30
1 + 5 ÷ 30 = 1.1667
- 2
Estimated 1RM (Epley)
1RM = Weight × (1 + Reps ÷ 30) · for 1 rep, 1RM = Weight
225 × 1.1667 = 262.5
- 3
Cross-check: Brzycki
1RM = Weight × 36 ÷ (37 − Reps)
225 × 36 ÷ (37 − 5) = 253.1
- 4
Working weight for 8 reps
Weight₈ = 1RM ÷ (1 + 8 ÷ 30)
262.5 ÷ 1.2667 = 207.2
- 1 rep262.5
- 2 reps246.1
- 3 reps238.6
- 5 reps225
- 8 reps207.2
- 10 reps196.9
- 12 reps187.5
Good to know: Epley and Brzycki are most accurate below about 10 reps; error grows with higher reps. The answer is in whatever unit you entered (kg or lb). Only attempt a true 1RM warmed up, with a spotter and solid technique.
One-Rep Max Calculator — how it works
The Epley and Brzycki formulas
Both convert a multi-rep set into a single-rep estimate. They agree closely and this tool shows both:
| Formula | 1RM estimate |
|---|---|
| Epley | weight × (1 + reps ÷ 30) |
| Brzycki | weight × 36 ÷ (37 − reps) |
The headline figure uses Epley; Brzycki is shown alongside so you can see the small spread between methods.
Training weights from your 1RM
Programs usually call for a rep range, not a single max. Working the Epley formula backwards gives the weight for any target reps:
| Reps | Approx. % of 1RM |
|---|---|
| 1 | 100% |
| 2 | ~94% |
| 3 | ~90% |
| 5 | ~86% |
| 8 | ~79% |
| 10 | ~75% |
| 12 | ~71% |
The tool lists the actual weights for these rep targets, so you can load the bar directly.
Accuracy and safety
Estimates are most reliable at low reps — around 2 to 6. Past about 10 reps, fatigue and technique start to distort the result and the 1RM is over-estimated. Use a weight you lifted with good form and a rep or two left in the tank, and always warm up and use a spotter for heavy lifts.
Worked example
Suppose you bench-pressed 100 kg for 5 clean reps. Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg as your estimated 1RM, and Brzycki gives 100 × 36 ÷ 32 = 112.5 kg — close agreement. Working back from the Epley max, a set of 3 would use about 105 kg and a set of 10 about 87 kg. If a program says “3 × 5 at 80% of 1RM”, that’s roughly 93 kg.
Estimated one-rep max by weight lifted and reps (Epley)
| Weight | 3 reps | 5 reps | 8 reps | 10 reps |
|---|---|---|---|---|
| 40 kg | 44 kg | 46.7 kg | 50.7 kg | 53.3 kg |
| 50 kg | 55 kg | 58.3 kg | 63.3 kg | 66.7 kg |
| 60 kg | 66 kg | 70 kg | 76 kg | 80 kg |
| 70 kg | 77 kg | 81.7 kg | 88.7 kg | 93.3 kg |
| 80 kg | 88 kg | 93.3 kg | 101.3 kg | 106.7 kg |
| 90 kg | 99 kg | 105 kg | 114 kg | 120 kg |
| 100 kg | 110 kg | 116.7 kg | 126.7 kg | 133.3 kg |
| 120 kg | 132 kg | 140 kg | 152 kg | 160 kg |
| 140 kg | 154 kg | 163.3 kg | 177.3 kg | 186.7 kg |
1RM = weight × (1 + reps ÷ 30). Estimates get unreliable beyond about 10 reps.
Frequently asked questions
What is a one-rep max?+
It’s the heaviest weight you can lift for exactly one repetition of an exercise with good form. It measures maximal strength and is the basis most training programs use to prescribe working weights as a percentage.
How is 1RM estimated without a max test?+
From a sub-maximal set. Formulas like Epley (weight × (1 + reps ÷ 30)) and Brzycki convert a weight you lifted for several reps into a single-rep estimate, avoiding the risk and fatigue of a real max attempt.
How many reps should I use for the estimate?+
Fewer is more accurate — ideally 2 to 6 reps. Beyond about 10 reps the estimate becomes unreliable and tends to over-state your max, because muscular endurance rather than pure strength starts to dominate.
Why do Epley and Brzycki give different numbers?+
They’re different curve fits to real lifting data, so they diverge slightly — usually by only a few percent. Epley tends to read a touch higher at high reps. Seeing both gives you a sensible range rather than a single false-precise figure.
Is it safe to test my actual 1RM?+
Only with proper warm-up, good technique, a spotter and experience. For most people an estimate from a 3–5 rep set is safer and precise enough for programming. Never attempt a true max alone or without ramping up to it.
Sources
About this page
- Publisher:
- Kalkoro — Teknolojig Bilişim Teknolojileri A.Ş., İstanbul
- Written by:
- Kübra Yıldız — Editor (Health, nutrition, pregnancy, education, exam scores)
- Reviewed by:
- Furkan Tur — Editor
Parameters come from official sources; the last update date is shown at the bottom of the page.
Spotted a wrong result? Use the "Report a bug" button at the top of the page; every report is reviewed.
How we calculate and our accuracy policy →
This tool is for general information only and is not medical diagnosis, treatment or advice. Consult a physician for decisions about your health.
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