Strength · 2 min read

How to Estimate Your 1RM Without Testing a Max

Written by Coach Ohm · reviewed 2026-08-15

Try it: Working Weight Calculator — Estimate a 1RM from a real set, then get working weights and a warm-up ladder.

You need a one-rep max number to program percentages. You do not need to actually lift a one-rep max to get one.

Why not just test it

A true maximum attempt means maximal load with a technique that is degrading under it, usually with a spotter, followed by several days of compromised training. For a competing powerlifter that trade is part of the job. For everyone else it costs a week of quality training and carries injury risk to produce a number that an estimate would have given within a few per cent.

The two formulas

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

They disagree slightly and in opposite directions depending on rep count. The working weight calculator averages them, which is not more scientific — it just avoids inheriting the specific bias of either one.

The input that decides accuracy

Everything rests on the set you enter being genuinely close to failure. This is where the estimate usually goes wrong, and it goes wrong in the same direction every time: people enter a comfortable set.

A set of 5 you could have taken to 8 produces an estimate that is significantly too low. Every working weight derived from it is then too light, and you spend a training block under-loading. If you are unsure, assume you had more in reserve than it felt like, and treat the output as a floor to be tested rather than a ceiling.

Use 3 to 6 reps

Below three, you are close enough to a true max that the risk you were avoiding comes back. Above about ten, the estimate drifts upward because the limiting factor shifts from maximal force production toward muscular endurance — and how long someone can hold a submaximal load varies between people far more than maximal strength does.

Which lifts this works for

Best on compound barbell movements: squat, bench press, deadlift, overhead press. These have a well-understood load–rep relationship and enough stability for the pattern to hold.

Less reliable on isolation work and machines, where the resistance curve, the stabiliser demand and the machine's own leverage all interfere. You can still use it for choosing weights; just do not treat the number as meaningful in itself.

Re-test rather than recalculate

An estimate goes stale. A beginner outgrows it in weeks; an experienced lifter in a few months. Rather than adjusting the number on paper, put a real set back into the calculator every four to six weeks and let the working weights move with it.

What to do with the number

Percentages, not guesses. A 5×5 at 80 per cent, a top single at 90, back-off sets at 70 — these are only meaningful if the number they refer to is roughly right. See picking your working weight for how the percentages map to rep ranges.

A note if you are in a deficit

Expect the estimate to stall or slip late in a fat loss phase. That is not a failure of the programme. It is what happens when you are recovering on less energy, and holding your numbers roughly steady through a deficit is a good result rather than a disappointing one.

Questions I get asked

How accurate are these estimates?

Close enough to program from when the input set was genuinely near failure and in the 3 to 6 rep range. They are not close enough to base a competition attempt on.

Can I estimate from a set of 15?

You can, and the number will be inflated. Use it as a rough placeholder and re-test with something heavier when you can.