One Rep Max Calculator
Estimate your one-rep max (1RM) from a set you can complete, using the Epley and Brzycki formulas, plus a full percentage chart for your training. Runs in your browser.
Estimated one-rep max
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Training percentages
Target weights for common rep ranges, based on your estimated 1RM (Epley):
| Reps | % of 1RM | Weight |
|---|
Barbell plate loader
Plates to load on each side of the bar for a target weight:
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Show the math
Two widely used estimates from a sub-maximal set:
Epley: 1RM = w × (1 + reps ÷ 30)
Per side = (target − bar) ÷ 2, loaded heaviest plate first
Brzycki uses w × 36 ÷ (37 − reps). Estimates are most accurate under about 10 reps; beyond that, fatigue makes them drift. Never test a true max without a spotter and a proper warm-up.
What this does
A one-rep max calculator estimates your 1RM from a set you can complete, using the Epley and Brzycki formulas, plus a full percentage chart for programming your training.
How it works
Epley uses weight × (1 + reps ÷ 30); Brzycki uses weight × 36 ÷ (37 − reps). The tool shows both and an average so you do not have to attempt a true max.
Epley: 1RM = weight × (1 + reps ÷ 30)
How to use it
- Enter the weight you lifted.
- Enter the number of clean reps.
- Read your estimated one-rep max.
- Use the percentage chart to set working weights.
Understanding your result
Estimates are most accurate at lower reps (ideally under 10) because fatigue and technique drift reduce reliability above that. The chart gives weights for common rep targets without maxing out.
Example
Lifting 100 kg for 5 reps estimates a 1RM of about 117 kg.
Sources & methodology
Last updated .
Frequently asked questions
How is 1RM estimated?
From the weight and number of reps you can complete. The Epley formula uses weight × (1 + reps ÷ 30); Brzycki uses weight × 36 ÷ (37 − reps). The tool shows both and an average.
How many reps should I test with?
Estimates are most accurate at lower reps — ideally under 10. Above that, fatigue and technique drift make the prediction less reliable.
What is the percentage chart for?
It shows the weight for common rep targets (e.g. 5 reps at ~87% of 1RM) so you can program your sets without ever maxing out.
Do you store my lifts?
No. All math happens locally in your browser.
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