One Rep Max Calculator
Enter a weight and how many reps you lifted it for. You get your estimated one rep max — no max-out attempt needed.
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 95% | 108.9 kg | ~2 |
| 90% | 103.1 kg | ~4 |
| 85% | 97.4 kg | ~6 |
| 80% | 91.7 kg | ~8 |
| 75% | 85.9 kg | ~10 |
| 70% | 80.2 kg | ~12 |
How it works
The calculator uses the two most trusted estimation formulas. Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). Both were built from real lifter data and agree closely at low reps, so we show the average as your headline number.
Example: 100 kg for 5 reps gives 116.7 kg (Epley) and 112.5 kg (Brzycki) — an estimated max of about 114.5 kg.
Getting a good estimate
Use a recent, hard set where you stopped 0-1 reps short of failure. Sets of 3-6 reps give the most reliable numbers. Warm-up sets and easy sets will underestimate your max.
FAQ
What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift for a single rep with good form. It is the standard way to measure strength on lifts like the squat, bench press, and deadlift.
How accurate are 1RM formulas?
Very accurate in the 2-6 rep range, usually within a few percent. Above 10 reps the estimate gets rougher because endurance starts to matter more than pure strength. For the best estimate, use a heavy set of 3-5 reps.
Should I actually test my 1RM in the gym?
Most lifters don't need to. A true max attempt carries injury risk and takes a full session to recover from. Estimating from a heavy set of 3-5 gives you a number that is close enough to program with.
What's the difference between Epley and Brzycki?
They are two different regression formulas built from lifter data. Epley tends to estimate slightly higher at high reps, Brzycki slightly lower. This calculator shows both and averages them.
How do I use my 1RM in training?
Program your working sets as a percentage of it. Roughly: 90%+ for strength singles and doubles, 80-85% for 5-6 rep strength work, 70-75% for 8-12 rep muscle-building sets. The table above does the math for you.
Related
Stop doing 1RM math by hand
Buffro tracks your estimated one rep max on every exercise automatically — and ranks your strength from Beginner to Apex.