One-Rep Max (1RM) Calculator
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise. Knowing your 1RM helps you program training loads, track strength progress, and compare performance across different rep ranges.
This calculator estimates your 1RM using two well-known formulas — Epley and Brzycki — based on a sub-maximal lift. It also provides a percentage table so you can plan sets at the right intensity for your training goals.
How it works
Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight × 36 / (37 − reps). Both formulas are most accurate for rep ranges of 2–10.
Use cases
- Programming training loads based on percentage of 1RM
- Tracking strength progress over time without maximal testing
- Comparing strength across different rep ranges and exercises
- Planning periodized training cycles
Frequently asked questions
How do I calculate my 1RM without maxing out?
Lift a sub-maximal weight for as many clean reps as possible (ideally 2–10), then apply an estimation formula. The Epley formula is 1RM = weight × (1 + reps / 30) and the Brzycki formula is 1RM = weight × 36 / (37 − reps). This calculator applies both and shows you the results side by side.
What is the Epley formula for one-rep max?
The Epley formula estimates 1RM as weight × (1 + reps / 30). For example, lifting 100 kg for 5 reps gives an estimated 1RM of 100 × (1 + 5/30) ≈ 116.7 kg. It is one of the most widely used 1RM equations and is most accurate in the 2–10 rep range.
Which is more accurate, Epley or Brzycki?
Both formulas produce identical results at 10 reps and are considered reliable within the 2–10 rep range. Below 10 reps, Epley gives slightly higher estimates than Brzycki — for example, at 5 reps Epley multiplies the weight by about 1.167 versus 1.125 for Brzycki. Accuracy drops for both formulas beyond 10 reps, so use lower-rep sets for better estimates.
What percentage of my 1RM should I train with?
Training loads are typically programmed as percentages of 1RM: heavier loads around 85% and above with low reps are common for maximal strength work, while moderate loads roughly between 65% and 85% suit higher-rep hypertrophy training. This calculator includes a percentage table so you can plan sets at the right intensity for your goal.
Is it safe to test my true one-rep max?
Testing a true 1RM places maximal stress on muscles, joints, and connective tissue, so it carries more injury risk than estimating from sub-maximal sets — which is exactly what this calculator is for. If you do test, warm up thoroughly, use strict technique, and have a spotter or safety equipment. Beginners and anyone with health concerns should get guidance from a qualified coach or healthcare professional first.