One-Rep Max (1RM) Calculator
Enter the weight you lifted and the number of reps you completed, and the calculator instantly estimates your one-rep max (1RM) using four widely-cited formulas — Epley, Brzycki, Lombardi and Lander — plus a 50–95% training intensity table you can use to plan your next session. Switch between kg and lb, and share the URL with a coach or training partner.
Enter a positive weight and at least 1 rep.
Estimated 1RM
— kg
—
Average of 4 formulas
— kg
All formulas compared
-
Epley
— kg
-
Brzycki
— kg
-
Lombardi
— kg
-
Lander
— kg
Training intensity table
Suggested loads at each %1RM with the typical rep range coaches prescribe.
| Intensity | Load | Reps |
|---|---|---|
| 95% | — kg | ≤2 |
| 90% | — kg | 3–4 |
| 85% | — kg | 5–6 |
| 80% | — kg | 7–8 |
| 75% | — kg | 9–10 |
| 70% | — kg | 11–12 |
| 65% | — kg | 13–15 |
| 60% | — kg | 16–18 |
| 55% | — kg | 19–22 |
| 50% | — kg | 23+ |
Estimates are for programming, not a substitute for a true 1RM test — warm up properly and use a spotter for any heavy attempt.
Formula
Epley 1RM = w × (1 + r/30) Brzycki 1RM = w × 36 / (37 − r) Lombardi 1RM = w × r^0.10 Lander 1RM = 100 × w / (101.3 − 2.67123 × r) w = weight lifted (kg or lb); r = reps completed to failure
- · Estimates are for programming, not a substitute for a true 1RM test — warm up fully, use a spotter and progress conservatively when attempting heavy singles.
- · All four formulas work best at 1–10 reps. Above ~12 reps the relationship between fatigue and load is no longer linear, so prediction error grows quickly.
- · Brzycki blows up at r = 37 (the denominator hits zero). The widget falls back to the other formulas and surfaces a warning when reps are unrealistically high.
- · Choosing a formula: Epley is the most widely cited starting point for classic strength training; Lombardi tends to be conservative at higher reps; Lander appears in NSCA tables. If you want a single defensible number, take the average of the four.
- · The training intensity table (%1RM ↔ typical reps) is taken from the NSCA Essentials of Strength Training and Conditioning, 4th ed., Chapter 15.
- · Sources: Epley (1985), Brzycki (1993, JOPERD), Lombardi (1989), Lander (1985); see also Reynolds, Gordon, Robergs (2006, J Strength Cond Res) for a comparison of formula error.
Frequently asked
Which 1RM formula is the most accurate?
There is no single "best" formula — Reynolds, Gordon & Robergs (2006) compared several against actual 1RM tests in bench press and squat, and in the 1–10 rep range Epley and Brzycki both stayed within roughly ±5%, which is good enough for programming. Lombardi is more conservative at high reps, Lander tracks closely with Brzycki. In practice: prefer Brzycki when the rep count is 1–6; switch to Epley around 8–10; or just take the average of all four for a defensible single number. If your prediction is off by more than ~5% from a real test, factors like fatigue, technique drift or stimulant use are usually the cause — re-test.
Why are estimates unreliable above ~10 reps?
The formulas are empirical regressions fit mostly to data in the 1–10 rep range. Past ~10 reps the limiting factor shifts from neuromuscular force production to muscular endurance and metabolic clearance, which is no longer a linear relationship — and individual variance widens fast. Practical advice: pick a load you can hit for 3–8 clean reps when you want a meaningful 1RM estimate. At 15+ reps you are testing endurance, not strength, and the whole 1RM-prediction frame is less appropriate.
Can I program my whole training plan from %1RM?
Yes — classic periodisation systems (Sheiko, Smolov, Wendler 5/3/1) all build sessions from %1RM. Use this calculator to set your starting 1RM, then read the intensity table for the load at each %1RM band. Two cautions: (1) 1RM drifts with technique, sleep and nutrition, and each lift (squat, bench, deadlift, press) has its own 1RM — never share one percentage across lifts. (2) Re-test or re-estimate every 4–8 weeks, and let RPE / RIR fine-tune day to day — 80% on a fresh day is not the same as 80% on a fatigued day.
Are kg and lb conversions exact?
The widget uses the exact NIST conversion 1 lb = 0.45359237 kg, so switching units introduces no rounding error. The formulas are unit-invariant — feeding the weight in your chosen unit straight into the formula gives a 1RM in the same unit, and the two answers match exactly when converted back. Common reference points: 225 lb ≈ 102.06 kg, 315 lb ≈ 142.88 kg, 405 lb ≈ 183.71 kg.
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