What it does
Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Testing it directly is tiring and carries more risk, so most lifters estimate it from a heavier set of a few reps. This tool uses two well-known formulas, Epley and Brzycki, shows their average, and builds a table of 50% to 100% of that number so you can plan your working sets.
Everything runs in your browser and nothing is sent anywhere. To plan the energy side of training, use the calorie calculator; for runs, the pace calculator.
How to use it
- Type the weight you lifted and pick kg or lb. Switching the unit converts the weight.
- Type how many reps you did, taken close to failure.
- Read the three estimates, then use the table for training weights.
What each setting does
- Weight lifted: the load on the bar or machine for the set.
- Reps done: whole reps in that set. One rep gives the weight itself.
- Round the table to: rounds table weights to the nearest 1, 2.5 or 5 so they match the plates you have, or leaves them at one decimal.
- Reset: brings back the example.
The About reps column turns Epley around, reps ≈ 30 × (100 / percent − 1), so it is a rough guide only. With more than 12 reps a warning shows, because both formulas drift apart and lose accuracy on long sets.
Worked example
You squat 100 kg for 5 reps.
- Epley: 100 × (1 + 5/30) = 116.7 kg
- Brzycki: 100 × 36 / (37 − 5) = 100 × 36 / 32 = 112.5 kg
- Average: (116.7 + 112.5) / 2 = 114.6 kg
The 90% row is 114.6 × 0.9 = 103.1 kg, rounded to the nearest 2.5 gives 102.5 kg, for about 3 reps.
FAQs
Which formula is better? Neither wins for everyone. They agree closely for sets of 2 to 10 reps; the average is a sensible middle.
Why does the warning appear above 12 reps? Long sets test endurance as much as strength, so the estimate gets less reliable.
Should I test my real max? Only with a spotter or safety bars and after a good warm-up. This tool is a planning estimate, not advice for your body.
Does it remember my lifts? No. Nothing is stored.
Where the numbers come from
- Epley B (1985). Poundage chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises (1RM = w × (1 + r/30)).
- Brzycki M (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance 64(1): 88–90 (1RM = w × 36 / (37 − r)).
- Table, rounding and rep estimates are fibub's own working. 1 lb = 0.45359237 kg.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Read more on the Blog
- How to estimate your max lift without testing it(the full guide)
Last updated 2026-11-10.