Podsumowanie
The one-repetition maximum (1RM) is the heaviest weight you can lift for exactly one rep with proper form. It is the gold standard for measuring maximal strength. Because testing a true 1RM carries injury risk and requires extensive warm-up, prediction formulas estimate it from a lighter weight lifted for multiple reps.
This calculator uses three well-established formulas — Epley (1985), Brzycki (1993), and Lander (1985) — and averages them for a more robust estimate. All three are most accurate between 1–10 reps.
Jak to działa
You enter a weight you lifted and the number of reps you completed before failure. Each formula applies a different mathematical model to extrapolate what your max single rep would be. The calculator then builds a training percentage chart showing what weights to use for different rep ranges.
The three formulas produce slightly different estimates. Epley tends to give higher predictions at low reps, while Brzycki is more conservative. At exactly 10 reps, Epley and Brzycki return identical results. Averaging all three gives a balanced estimate.
The formulas
Epley (1985)
Where
The most widely used formula in commercial gyms and fitness apps. Originally published by Boyd Epley at the University of Nebraska-Lincoln.
Brzycki (1993)
Where
Published by Matt Brzycki in the Journal of Physical Education, Recreation & Dance (JOPERD). NCAA validated. Equivalent to weight ÷ (1.0278 − 0.0278 × reps).
Lander (1985)
Where
Published by Jeff Lander in the NSCA Journal. Produces estimates between Epley and Brzycki for most inputs.
Training percentage chart
The calculator also generates a loading chart based on the NSCA Training Load Chart (Baechle & Earle, 2008):
| % of 1RM | Max Reps | Training goal |
|---|---|---|
| 100% | 1 | Max strength |
| 95% | 2 | Strength |
| 93% | 3 | Strength |
| 90% | 4 | Strength |
| 87% | 5 | Strength |
| 85% | 6 | Strength/Hypertrophy |
| 83% | 7 | Hypertrophy |
| 80% | 8 | Hypertrophy |
| 77% | 9 | Hypertrophy |
| 75% | 10 | Hypertrophy |
| 70% | 12 | Hypertrophy/Endurance |
| 65% | 15 | Endurance |
Przykład obliczeniowy
100 kg lifted for 5 reps
Epley formula
= 116.7 kg
Brzycki formula
= 112.5 kg
Lander formula
= 113.7 kg
Average 1RM
= 114.3 kg
Result
Estimated 1RM = 114 kg (average of 3 formulas)
Objaśnienie danych wejściowych
- Weight lifted — the weight you used for your set, in kg or lbs. The formulas are unit-agnostic: enter kg and get kg back, enter lbs and get lbs back.
- Reps completed — number of full repetitions completed to failure (or very near failure). Must be honest — stopping 3 reps short of failure will underestimate your 1RM.
- Units — metric (kg) or imperial (lbs). Switches the slider range and labels but does not affect the calculation.
Objaśnienie wyników
- Estimated 1RM — the average of all three formulas. This is the headline number.
- Individual formula results — Epley, Brzycki, and Lander estimates shown separately so you can see the spread.
- Training percentage chart — a table showing the weight to use for different rep ranges, based on the NSCA guidelines.
Założenia i ograniczenia
- Most accurate at 1–10 reps. Brzycki (1993) noted that the relationship between load and reps-to-fatigue is “near linear” up to 10 reps, but becomes exponential beyond that. Above 10 reps, estimates may overpredict by 10–15% or more.
- Assumes reps to failure. If you stopped with reps in reserve, the prediction will underestimate your true 1RM.
- Exercise-specific. A 1RM estimated from bench press cannot be transferred to squat or deadlift. Each lift has its own 1RM.
- Assumes good form. The formulas assume full range of motion and consistent technique. Partial reps, bouncing, or excessive body English will inflate the estimate.
- Individual variation. Muscle fibre type, training history, and fatigue tolerance all affect the reps-to-load relationship. Some people perform more reps at a given percentage of 1RM than others.
- Not a substitute for testing. For competition preparation, a carefully supervised 1RM test is more accurate than any prediction formula.
Weryfikacja
| Test case | Input | Epley | Brzycki | Lander | Average |
|---|---|---|---|---|---|
| Intermediate bench | 100 kg × 5 | 116.7 | 112.5 | 113.7 | 114.3 |
| Moderate reps | 80 kg × 10 | 106.7 | 106.7 | 107.3 | 106.9 |
| Low reps | 60 kg × 3 | 66.0 | 63.5 | 64.3 | 64.6 |
All values verified by hand calculation and cross-checked against reference calculators (athlegan.com, calculator.net, topendsports.com).
Sources
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