Tools / Strength
One-rep max
calculator.
Turn a recorded set into an estimated 1RM. See two formulas side by side, and the assumptions behind each number.
02 / Estimated one-rep max
93.3 kg
Epley estimate. A model output, not a tested max.
- Epley
- 93.3 kg
- Brzycki
- 90 kg
The difference between formulas is not a confidence interval. Neither formula is guaranteed to be closer for your lift.
Calculated in your browser. These tools do not send or save your inputs.
03 / Explore the model
Rep-max estimate table.
Each row is the exact inverse of the selected formula before rounding. The percentage is the row’s estimated load divided by estimated 1RM. This is not a recommended lifting plan or a guarantee you can complete these reps.
| Target reps | % of estimated 1RM | Estimated load |
|---|---|---|
| 1 | 100% | 93.3 kg |
| 2 | 93.8% | 87.5 kg |
| 3 | 90.9% | 84.8 kg |
| 4 | 88.2% | 82.4 kg |
| 5 | 85.7% | 80 kg |
| 6 | 83.3% | 77.8 kg |
| 7 | 81.1% | 75.7 kg |
| 8 | 78.9% | 73.7 kg |
| 9 | 76.9% | 71.8 kg |
| 10 | 75% | 70 kg |
Keep the record going
Your next set.
A history to build on.
Flame keeps previous lifts beside today’s sets and your completed sessions together. This web tool stays separate; your entries are not automatically transferred to the app.
The calculation
See the working.
Let w be weight and r be completed repetitions. For 2–10 reps, this tool uses:
- Epley: estimated 1RM = w × (1 + r / 30).
- Brzycki: estimated 1RM = w × 36 / (37 − r).
With 80 kg × 5: Epley gives 80 × (1 + 5 / 30) = 93.3 kg; Brzycki gives 80 × 36 / 32 = 90 kg.
For a recorded single, both outputs equal the entered weight. This is an explicit convention: we do not apply Epley’s usual extrapolation to a one-rep set. A submaximal single still does not reveal your true max.
To reverse Epley, divide estimated 1RM by (1 + target reps / 30). To reverse Brzycki, multiply it by (37 − target reps) / 36. For example, a 100 kg Brzycki 1RM corresponds to 88.9 kg for 5 reps before practical equipment rounding.
Use the number well
An estimate,
with limits.
Rep-based estimates vary with the exercise, individual, range of motion, fatigue, equipment, and how close the recorded set was to your repetition limit. This tool limits inputs and the rep table to 10 reps; this limit is not a promise of accuracy within that range.
The displayed decimal helps compare formulas. It does not mean your actual capacity is known to 0.1 kg or lb. The table does not round to your available plates.
Compare estimates from the same lift and loading convention over time. Assisted exercises and bodyweight movements need a separate, consistent load model; entering external weight alone does not account for body mass or assistance.
These calculations are descriptive estimates, not lifting prescriptions. Do not choose a maximal attempt based on a calculator alone.
Method & references.
Reviewed November 4, 2026. Brzycki is implemented using the unrounded ratio form 36 / (37 − reps), rather than rounded decimal coefficients. Only the two equations shown above are used; no average is presented as a more accurate result.
- Matt Brzycki (1993), Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue, the original journal article.
- Royal College of Physicians, Pulmonary Rehabilitation audit FAQs, August 2025, documents the Epley equation in its strength assessment guidance. This is a formula reference, not evidence that it is accurate for every gym exercise.
The examples on this page are illustrative calculations, not customer results.