Which formula does this use?

It averages the Epley and Brzycki formulas, two of the most widely used 1RM estimates, and shows each one separately. Estimates are most accurate for sets of about 10 reps or fewer.

What are the training percentages for?

Strength programmes often prescribe work as a percentage of your 1RM — for example 5 reps at 87% or 8 reps at 80%. The table converts your estimated max into target weights for common rep ranges.

Why do Epley and Brzycki give slightly different numbers?

They are different regression models fitted to different lifting data. Epley tends to read slightly higher at high reps, Brzycki slightly lower. Averaging them reduces the bias of relying on either one alone.

Is the estimate accurate at high reps?

It is most accurate for sets of about 10 reps or fewer. Beyond 10–12 reps, fatigue and technique introduce more error, and Brzycki even breaks down mathematically as reps approach 37.

Should I test my true 1RM instead?

For most lifters an estimate is safer. Maximal singles carry higher injury risk and need a spotter and full warm-up. Estimating from a set of 3–6 reps gives a close figure without the risk.

Is my lift data uploaded?

No. The calculation runs entirely in your browser and nothing is uploaded or stored.

One Rep Max Calculator

Your one-rep max (1RM) is the most weight you can lift for a single repetition with good form. Rather than testing it directly — which is risky and needs a spotter — this calculator estimates it from a set you have already done. Enter the weight and reps, and it averages two of the most widely used formulas for a reliable figure, then builds a table of training weights.

How it works

The tool computes two established 1RM estimates and averages them:

Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)

The headline figure is (Epley + Brzycki) ÷ 2. It accepts 1–30 reps but is most accurate at 10 reps or fewer. From the estimated max it then derives target weights using standard percentages of 1RM (for example 87% for a 5-rep set).

Example

You bench press 100 kg for 5 reps:

Epley: 100 × (1 + 5/30) = 116.7 kg
Brzycki: 100 × 36 ÷ (37 − 5) = 112.5 kg
Estimated 1RM (average): ≈ 114.6 kg

Reps	% of 1RM	Target weight
1	100%	114.6 kg
3	90%	103.1 kg
5	87%	99.7 kg
8	80%	91.6 kg
12	70%	80.2 kg

Everything runs in your browser; nothing is uploaded.