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1RM calculator — estimate your one rep max.
Your one rep max (1RM) is the most weight you can lift for a single rep. This calculator estimates it from any set by averaging the Epley and Brzycki formulas, then builds a full percentage table so you can program every working set. Enter a weight and reps below — the result updates instantly, no signup.
Your percentage training table
The weight to load at each % of your max, with an approximate rep range to program from.
The formulas, explained.
No black box. The estimate is the average of the two most validated strength equations — here they are in full.
1RM = W × (1 + R ÷ 30) Reads slightly high at higher reps. 100 kg × 5 → 117 kg.
1RM = W × 36 ÷ (37 − R) Reads slightly low at higher reps. 100 kg × 5 → 113 kg.
1RM = (Epley + Brzycki) ÷ 2 The balanced average — here, about 115 kg, where W is weight and R is reps.
Most accurate for sets of 1 to 10 reps. Above 10 reps, fatigue and conditioning skew the estimate, so use it as a guide. Brzycki is undefined at 37 reps and beyond, so this tool caps the input at 36.
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How accurate is a 1RM calculator?
For sets of 1 to 10 reps the estimate is usually within about 5 to 10 percent of a true tested max. Accuracy drops above 10 reps, where fatigue and conditioning matter more than pure strength, so treat high-rep estimates as a rough guide rather than a hard number.
Which 1RM formula is best?
No single formula wins for everyone. Epley tends to read slightly high and Brzycki slightly low, so this calculator averages the two for a balanced estimate. Both are among the most validated equations for strength training and agree closely in the 1 to 10 rep range.
How do I use % of 1RM to train?
Pick the percentage that matches your goal: roughly 85 to 100 percent for max strength (1 to 5 reps), 70 to 85 percent for hypertrophy (6 to 12 reps), and 50 to 70 percent for technique and endurance work. The percentage table below gives you the exact weight for each band.
Should I ever test a true 1RM?
Occasionally, yes, but you rarely need to. A true 1RM test is fatiguing and carries more injury risk, so most lifters estimate from a 3 to 5 rep set and only test a real single when peaking for a meet or a milestone. Always warm up thoroughly and use a spotter.
Is this 1RM calculator free?
Yes, completely free with no signup. Save the result to your Nishaana account and it auto-applies your estimated max to your next workout, so your percentage targets are filled in for you at the rack.
Save your 1RM. Track it.
Free in your browser — Nishaana auto-applies your max to every workout, so your percentage targets are filled in at the rack.
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