TOOL — 1RM CALCULATOR
Enter the weight and reps you lifted and get your estimated one-rep max (e1RM). No need to test a true 1RM to know roughly where you stand. It uses the same Epley formula as Tailrep itself.
Estimated 1RM
101.3kg
The estimate drifts as reps go up. Ten reps or fewer is the useful range.
Weights back-calculated from the estimated 1RM for each rep target. Useful when deciding what to load for the next set.
| Reps | % of 1RM | Weight |
|---|---|---|
| 1 | 97% | 101.3 kg |
| 2 | 94% | 95 kg |
| 3 | 91% | 92.1 kg |
| 4 | 88% | 89.4 kg |
| 5 | 86% | 86.9 kg |
| 6 | 83% | 84.4 kg |
| 8 | 79% | 80 kg |
| 10 | 75% | 76 kg |
| 12 | 71% | 72.4 kg |
A 1RM (one repetition maximum) is the heaviest weight you can lift once. Testing it is risky and taxing, which makes it a poor fit for everyday training.
That's what e1RM is for. It estimates your 1RM from an ordinary set like "80 kg × 8". Because it puts every set on one scale, it tells you whether you're actually getting stronger even when weight and reps keep changing.
This calculator uses the Epley formula. Brzycki and Lombardi are common alternatives; Epley is used here for how closely it tracks real lifts in the low-rep range and for how easy it is to reason about.
1RM = weight × (1 + reps ÷ 30)
At one rep the lifted weight is the 1RM. The higher the rep count, the wider the margin of error.