Estimated one-rep max: what it is and how to work it out

Your one-rep max is the heaviest weight you could lift once. Testing it for real is tiring and not necessary. An estimated one-rep max works it out from an ordinary set.

Why it is useful

It lets you compare sets with different reps. Is 60 kg for 10 reps better than 65 kg for 6? The estimate turns both into one number.

The formula

Glowra uses the Epley formula:

estimated max = weight × (1 + reps ÷ 30)

Above 12 reps the estimate becomes unreliable, so Glowra counts any longer set as 12.

Worked examples

Set	Sum	Estimated max
60 kg × 10	60 × (1 + 10 ÷ 30)	80 kg
65 kg × 6	65 × (1 + 6 ÷ 30)	78 kg
70 kg × 5	70 × (1 + 5 ÷ 30)	81.7 kg
40 kg × 12	40 × (1 + 12 ÷ 30)	56 kg
100 kg × 3	100 × (1 + 3 ÷ 30)	110 kg

So 60 kg for 10 reps (80 kg) is a slightly stronger set than 65 kg for 6 (78 kg).

How to use it

Watch the trend over weeks, not single workouts. A line that climbs slowly is what you want.
Compare a lift with itself. Estimates for different exercises are not comparable.
Treat it as a guide. It is an estimate, not a promise of what you can lift once.

To move the number up, see when to add weight.

Glowra shares general fitness information only. It is not medical, health or diet advice. If you have an injury, a health condition or are pregnant, speak to a qualified professional before training.