One Rep Max Calculator
Lift a weight for reps, get your max — by the two formulas every strength coach uses — plus your training percentages.
Estimate your one rep max
The two formulas
Both convert a multi-rep set into an estimated single-rep maximum. They agree closely under 6 reps and drift apart above 10 — Epley runs slightly more generous at high reps. 225 lb for 5 reps estimates a 1RM around 262–253 lb depending on formula; this calculator shows both and the average, which is the sensible number to train from.
Why estimate instead of test
True max attempts are taxing, technically risky when fatigued, and unnecessary for most training purposes. A hard set of 3–5 reps, plugged into the formulas, gets within a few percent with a fraction of the strain — which is why nearly every percentage-based program (5/3/1, Texas Method, most powerlifting templates) runs on an estimated or "training max" rather than a fresh gym PR. Accuracy degrades past ~10 reps, where endurance contaminates the strength signal: estimate from sets of 3–6 for best results.
Using the percentages
The standard intensity map: 85–95% for low-rep strength work (1–5 reps), 70–85% for muscle-building sets of 6–12, 60–70% for volume, technique, and warm-ups. Many programs deliberately train off 90% of true max to keep bar speed and recovery healthy. Re-estimate every 4–6 weeks from a recent hard set rather than chasing the calculator's number on a bad day — the formula describes your strength; it doesn't owe it to you on demand.
Frequently asked questions
Which formula is more accurate?
Below 6 reps they're nearly identical. Brzycki tends to fit bench press data slightly better; Epley flatters squats and deadlifts at higher reps. The average of both is a robust practical choice.
Should beginners test a real 1RM?
Generally no — early strength gains are mostly skill acquisition, and maximal attempts before technique solidifies invite injury. Train with rep estimates for the first several months; the formulas track your progress fine.
Why is my real max lower than the estimate?
Singles are their own skill — bracing, psychology, and bar-path precision under maximal load. High-rep estimators also flatter endurance-leaning lifters. The gap closes with practice at heavier percentages.
Do these formulas work for every exercise?
Best for the barbell lifts they were built on (squat, bench, deadlift, press). For isolation moves and machines the estimates are rough, and for explosive lifts like cleans, rep math barely applies.
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The one rep max formulas — what the math means
A one-rep maximum (1RM) is the maximum weight you can lift for exactly one repetition with good form. Directly testing your 1RM is the most accurate method but carries injury risk, particularly for less experienced lifters. The sub-maximal estimation formulas let you calculate a predicted 1RM from a weight you can lift for multiple reps — typically 3–10 reps, where the formulas are most accurate.
The most widely used formulas:
Epley (1985): 1RM = Weight × (1 + Reps ÷ 30). Simple and widely used. At 225 lb for 5 reps: 225 × (1 + 5/30) = 225 × 1.167 = 262.5 lb.
Brzycki (1993): 1RM = Weight × (36 ÷ (37 − Reps)). Tends to be slightly more conservative. At 225 lb for 5 reps: 225 × (36/32) = 225 × 1.125 = 253 lb.
Lombardi (1989): 1RM = Weight × Reps^0.1. At 225 lb for 5 reps: 225 × 5^0.1 = 225 × 1.174 = 264 lb.
All three are estimates. Accuracy decreases significantly above 10 reps — higher rep sets involve more endurance factors that do not scale linearly to 1RM. The sweet spot for 1RM estimation is 3–6 reps at near-maximal effort.
How to use your 1RM for programming
Your 1RM gives you a reference point for setting training loads. Common percentage-based prescriptions: 85–95% for strength development (1–5 reps), 70–85% for hypertrophy (6–12 reps), 50–70% for muscular endurance (15+ reps). A lifter with a 300 lb squat 1RM doing a 5×5 program at 80% would train at 240 lb — heavy enough to drive strength adaptation without daily maximal effort.
Frequently asked questions
Which formula is most accurate?
For most lifters in the 3–6 rep range, the Epley and Brzycki formulas are both within 5% of actual 1RM. Brzycki tends to be slightly more conservative. For very strong lifters or powerlifters, direct 1RM testing after a proper warm-up protocol is more reliable than any formula.
Is testing 1RM directly safe?
For experienced lifters with good technique, a properly structured 1RM test is generally safe. Required: thorough warm-up, working up gradually (typically 4–6 progressively heavier warm-up sets), and a spotter for barbell movements. Beginners should avoid direct 1RM testing until they have established consistent technique and at least 6–12 months of training.
Why does my estimated 1RM feel higher than my actual max?
Formulas assume a consistent strength-endurance curve that does not hold for all individuals. Some people are "rep strong" — able to do more reps at a given percentage than average — which inflates 1RM estimates. Others fatigue more quickly. The formulas are averages; your personal curve may differ. Use the estimate as a ballpark, not a guarantee.
Can I use this for deadlift, bench press, and squat equally?
Yes — the formulas are exercise-agnostic. Note that 1RM varies significantly by exercise and individual. Most people's deadlift 1RM exceeds their squat, which exceeds their bench press. Using the same percentage for all three lifts is reasonable for programming purposes but won't produce identical relative intensities.
Disclaimer: These are estimation tools only. Maximal lifting carries injury risk. Consult a qualified strength coach before attempting maximal lifts, especially if you are new to resistance training.