1RM (One Repetition Maximum) is the maximum weight you can lift for a single repetition with proper form. It is the standard measure of strength in powerlifting and strength training.

Which formula is most accurate for 1RM?

Epley is most widely used and works well at low rep ranges (1–10). Brzycki is slightly more accurate for 1–6 reps. Using an average of multiple formulas gives the most reliable estimate.

One Rep Max Calculator

Calculate your one rep max (1RM) from any weight and rep count using 6 validated formulas.

Weight unit

Kilograms (kg)

Pounds (lbs)

Weight lifted (kg)

Reps completed

Estimated 1RM (average)

115.8 kg

By formula

Formula	1RM
Epley	116.7 kg
Brzycki	112.5 kg
Lombardi	117.5 kg
Mayhew	119.0 kg
O'Conner	112.5 kg
Wathen	116.6 kg

Training percentages

% of 1RM	Weight (kg)	Rep range
100%	115.8	~1
95%	110.0	~2
90%	104.2	~4
85%	98.4	~6
80%	92.6	~8
75%	86.8	~10
70%	81.1	~12
65%	75.3	~15
60%	69.5	~17
55%	63.7	~20
50%	57.9	~25

One Rep Max (1RM) Calculator

The 1RM Calculator estimates the maximum weight you can lift for a single repetition based on a submaximal lift. It uses six well-validated formulas and averages them for a more reliable result.

Key formulas

Epley: weight × (1 + reps/30) — most widely used
Brzycki: weight × 36/(37 − reps) — best accuracy at low reps
Lombardi: weight × reps^0.10

Training zones

90–100% 1RM: Maximal strength (1–3 reps)
75–85% 1RM: Strength/hypertrophy (6–10 reps)
60–75% 1RM: Hypertrophy/endurance (12–20 reps)