Estimate the maximum weight you can lift for one repetition from a set you already completed. Enter the load, how many reps you made (1–10), and optionally the output unit and formula. The result includes a repetition chart and a percentage-of-1RM table you can use to plan training loads.
Use the estimate consistently
Prediction error depends on the exercise, number of repetitions, technique, training experience, and whether the set was truly near maximum effort. Use one formula for trend tracking and treat the percentage table as load arithmetic, not a promise that a specific load will produce a specific adaptation.
Examples
100 kg for 5 reps (Epley)
100 × (1 + 5 / 30) = 100 × 35 / 30 = 116.7 kg. At that 1RM, five reps is about 86% (100.0 kg), 10 reps about 75% (87.5 kg), and 85% of 1RM is 99.2 kg for an estimated 5 reps.
225 lb for 8 reps (Epley)
225 × (1 + 8 / 30) = 225 × 38 / 30 = 285.0 lb.
Same 100 kg × 5 set, result in pounds
116.7 kg converts at 1 lb = 0.45359237 kg to 257.2 lb. Brzycki on the same set is 112.5 kg; Lombardi is 117.5 kg.
Formula
Three formulas estimate 1RM from weight lifted (W) and repetitions (r):
Epley: 1RM = W × (1 + r / 30)
Brzycki: 1RM = W × 36 / (37 − r)
Lombardi: 1RM = W × r^0.10
Epley and Brzycki return the same value at 10 reps. The repetition table inverts the chosen formula so each row is the load that would produce the same 1RM; the 1-rep row is always 100% of the estimate. The percentage table multiplies the 1RM by 100%…50% and truncates the inverted formula to a whole-rep count.
These numbers are estimates. A true 1RM test should only be attempted with solid technique, a spotter, and enough rest between attempts. When in doubt, train below the estimate.
Sources
- LeSuer et al.: Validation of submaximal 1RM equations — prediction validity changes with repetition count.
- Grgic et al.: 1RM test-retest reliability systematic review — reliability and factors that affect testing.