How to use it
- Choose kilograms or pounds.
- Enter the weight you lifted and the reps you completed (1 to 30), keeping a rep or two in reserve is fine but a set to near failure gives the best estimate.
- Read the three estimates, their average and the table of loads by reps.
Formulas
With weight w and reps r:
- Epley: 1RM = w × (1 + r ÷ 30)
- Brzycki: 1RM = w × 36 ÷ (37 − r)
- Lombardi: 1RM = w × r^0.10
For a single rep the weight itself is the max. The table inverts the formulas to give the percentage of 1RM for each rep count: Epley 1 ÷ (1 + r ÷ 30), Brzycki (37 − r) ÷ 36 and Lombardi r^−0.10. The load is your average estimated 1RM times the average of the three percentages.
Worked example
You lifted 100 kg for 5 reps:
- Epley: 100 × (1 + 5 ÷ 30) = 116.7 kg
- Brzycki: 100 × 36 ÷ 32 = 112.5 kg
- Lombardi: 100 × 5^0.1 = 117.5 kg
- Average: 115.5 kg
For 10 reps Epley and Brzycki both say 75% of 1RM.
Limits and tips
- Prediction formulas were fitted on particular exercises and groups. They tend to be more reliable for big compound lifts than for isolation exercises.
- The more reps you do, the less reliable the estimate. Above about 10 reps, treat it as rough.
- Lift with a spotter or safety arms, and warm up well before heavy sets. If you are unsure whether heavy lifting is safe for you, ask a doctor or qualified coach.