1RM calculator
Estimate your one-rep max from any set of 1–12 reps — no max attempt needed. Results update as you type.
Training weights by % of 1RM
| % of 1RM | Weight | ≈ Reps |
|---|---|---|
| 100% | – | – |
| 95% | – | – |
| 90% | – | – |
| 85% | – | – |
| 80% | – | – |
| 75% | – | – |
| 70% | – | – |
| 65% | – | – |
| 60% | – | – |
| 55% | – | – |
| 50% | – | – |
Reps are estimated with the Epley formula and vary by exercise and experience.
How is 1RM calculated?
A one-rep max estimate predicts the heaviest single rep you could lift from a set of several reps. This calculator uses the two most common formulas and shows their average:
Epley
1RM = weight × (1 + reps ÷ 30)
Brzycki
1RM = weight × 36 ÷ (37 − reps)
Example: 100 kg × 5 reps → Epley 116.7 kg, Brzycki 112.5 kg, average about 115 kg. Both formulas agree closely up to 10 reps; above that, estimates become less reliable. More in the guide how to calculate your 1RM without maxing out.
1RM — frequently asked questions
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single, full repetition of an exercise with good form. It's the standard way to measure strength and to set training weights as a percentage.
How do you calculate 1RM without maxing out?
Lift a weight you can handle for 2–10 good reps, then plug the weight and reps into a formula. The Epley formula is 1RM = weight × (1 + reps ÷ 30). For example, 100 kg for 5 reps gives an estimated 1RM of about 117 kg.
Which 1RM formula is most accurate?
Epley and Brzycki are the most widely used and give almost the same result up to about 10 reps. Both get less accurate above 10–12 reps, so use a heavier set for the best estimate.
How often should I test my 1RM?
You don't need to test it directly. Estimating from your regular working sets lets you follow your strength every session without the fatigue and risk of a true max attempt.
Can an app track my estimated 1RM automatically?
Yes. Gym Companion calculates your estimated 1RM (Epley) from every set you log and shows it as a progress chart over 1 month, 3 months or all time. See progress tracking.
Watch your 1RM grow.
Gym Companion estimates your 1RM from every set and charts your progress — free on iPhone.
