1RM formula comparison

1RM Formula Comparison

The useful answer is not one exact number. Compare Epley, Brzycki, Lombardi, O'Conner, Mayhew, Wathan, and Lander, then treat the spread as a confidence interval for programming.

7 formulas

Formula spread

Training recommendation

Which 1RM formula is most useful?

Brzycki is often the best default for programming because it stays conservative, especially when reps climb above five. Epley and Wathan can be useful for experienced lifters who know how close to failure the set was. For most lifters, the best answer is the cluster: use the lower end when technique was uncertain, and use the middle when the set was clean.

When seven formulas agree within a narrow range, the estimate is more trustworthy. When the range is wide, the input set is probably too high-rep, too far from failure, or too dependent on the movement standard.

Formula reference

Scroll table horizontally

Formula	Equation	Best use	Estimate style
Epley	`1RM = w x (1 + r / 30)`	2-8 reps	practical default; often higher than Brzycki as reps rise
Brzycki	`1RM = w x 36 / (37 - r)`	1-6 reps	conservative; often lower than Epley and Wathan
Lombardi	`1RM = w x r^0.10`	2-10 reps	non-linear; often near the middle for common rep ranges
O'Conner	`1RM = w x (1 + 0.025r)`	2-8 reps	conservative linear estimate; often close to Brzycki
Mayhew	`1RM = 100w / (52.2 + 41.9 x e^(-0.055r))`	2-10 reps	research-derived curved model; often useful as an upper-body cross-check
Wathan	`1RM = 100w / (48.8 + 53.8 x e^(-0.075r))`	2-10 reps	curved model; often near Epley for moderate reps
Lander	`1RM = 100w / (101.3 - 2.67123r)`	2-10 reps	middle estimate; often between Brzycki and Epley

Example 1: 100 kg x 5 reps

A typical moderate-rep strength set where most formulas should converge.

Confidence interval: 112.5 kg - 119 kg. Mean: 115.5 kg. Conservative formula: Brzycki at 112.5 kg. Highest formula: Mayhew at 119 kg.

Scroll table horizontally

Formula	Calculation	Estimate	Training use
Epley	`100 x (1 + 5 / 30)`	116.7 kg	Confirm before using for heavy work
Brzycki	`100 x 36 / (37 - 5)`	112.5 kg	Safer training max input
Lombardi	`100 x 5^0.10`	117.5 kg	Confirm before using for heavy work
O'Conner	`100 x (1 + 0.025 x 5)`	112.5 kg	Safer training max input
Mayhew	`100 x 100 / (52.2 + 41.9 x e^(-0.055 x 5))`	119 kg	Confirm before using for heavy work
Wathan	`100 x 100 / (48.8 + 53.8 x e^(-0.075 x 5))`	116.6 kg	Confirm before using for heavy work
Lander	`100 x 100 / (101.3 - 2.67123 x 5)`	113.7 kg	Safer training max input

Example 2: 225 lb x 8 reps

A higher-rep bench-style example where aggressive formulas begin to separate.

Confidence interval: 270 lb - 287.3 lb. Mean: 280.6 lb. Conservative formula: O'Conner at 270 lb. Highest formula: Wathan at 287.3 lb.

Scroll table horizontally

Formula	Calculation	Estimate	Training use
Epley	`225 x (1 + 8 / 30)`	285 lb	Confirm before using for heavy work
Brzycki	`225 x 36 / (37 - 8)`	279.4 lb	Safer training max input
Lombardi	`225 x 8^0.10`	277 lb	Safer training max input
O'Conner	`225 x (1 + 0.025 x 8)`	270 lb	Safer training max input
Mayhew	`100 x 225 / (52.2 + 41.9 x e^(-0.055 x 8))`	284.1 lb	Confirm before using for heavy work
Wathan	`100 x 225 / (48.8 + 53.8 x e^(-0.075 x 8))`	287.3 lb	Confirm before using for heavy work
Lander	`100 x 225 / (101.3 - 2.67123 x 8)`	281.5 lb	Confirm before using for heavy work

Example 3: 60 kg x 3 reps

A low-rep example where almost every formula lands close together.

Confidence interval: 63.5 kg - 68.4 kg. Mean: 65.6 kg. Conservative formula: Brzycki at 63.5 kg. Highest formula: Mayhew at 68.4 kg.

Scroll table horizontally

Formula	Calculation	Estimate	Training use
Epley	`60 x (1 + 3 / 30)`	66 kg	Confirm before using for heavy work
Brzycki	`60 x 36 / (37 - 3)`	63.5 kg	Safer training max input
Lombardi	`60 x 3^0.10`	67 kg	Confirm before using for heavy work
O'Conner	`60 x (1 + 0.025 x 3)`	64.5 kg	Safer training max input
Mayhew	`100 x 60 / (52.2 + 41.9 x e^(-0.055 x 3))`	68.4 kg	Confirm before using for heavy work
Wathan	`100 x 60 / (48.8 + 53.8 x e^(-0.075 x 3))`	65.4 kg	Safer training max input
Lander	`100 x 60 / (101.3 - 2.67123 x 3)`	64.3 kg	Safer training max input

Example 4: 315 lb x 3 reps

A heavier strength example suitable for powerlifting percentage planning.

Confidence interval: 333.5 lb - 359.1 lb. Mean: 344.3 lb. Conservative formula: Brzycki at 333.5 lb. Highest formula: Mayhew at 359.1 lb.

Scroll table horizontally

Formula	Calculation	Estimate	Training use
Epley	`315 x (1 + 3 / 30)`	346.5 lb	Confirm before using for heavy work
Brzycki	`315 x 36 / (37 - 3)`	333.5 lb	Safer training max input
Lombardi	`315 x 3^0.10`	351.6 lb	Confirm before using for heavy work
O'Conner	`315 x (1 + 0.025 x 3)`	338.6 lb	Safer training max input
Mayhew	`100 x 315 / (52.2 + 41.9 x e^(-0.055 x 3))`	359.1 lb	Confirm before using for heavy work
Wathan	`100 x 315 / (48.8 + 53.8 x e^(-0.075 x 3))`	343.3 lb	Safer training max input
Lander	`100 x 315 / (101.3 - 2.67123 x 3)`	337.7 lb	Safer training max input

Example 5: 140 kg x 10 reps

A high-rep example that shows why estimates become less reliable near the upper limit.

Confidence interval: 175 kg - 188.6 kg. Mean: 183.5 kg. Conservative formula: O'Conner at 175 kg. Highest formula: Wathan at 188.6 kg.

Scroll table horizontally

Formula	Calculation	Estimate	Training use
Epley	`140 x (1 + 10 / 30)`	186.7 kg	Confirm before using for heavy work
Brzycki	`140 x 36 / (37 - 10)`	186.7 kg	Confirm before using for heavy work
Lombardi	`140 x 10^0.10`	176.2 kg	Safer training max input
O'Conner	`140 x (1 + 0.025 x 10)`	175 kg	Safer training max input
Mayhew	`100 x 140 / (52.2 + 41.9 x e^(-0.055 x 10))`	183.3 kg	Safer training max input
Wathan	`100 x 140 / (48.8 + 53.8 x e^(-0.075 x 10))`	188.6 kg	Confirm before using for heavy work
Lander	`100 x 140 / (101.3 - 2.67123 x 10)`	187.7 kg	Confirm before using for heavy work

Training recommendation

For low-rep sets of one to three, most formulas converge and the mean is usually usable. For four to six reps, use Brzycki, Epley, or the formula mean. For seven to ten reps, use the lower third of the range. Above ten reps, retest with a heavier set before using the number for percentage-based training.

For lift-specific decisions, use the lower estimate when squat depth changes, bench pause disappears, deadlift grip becomes the limiter, or overhead press turns into a push press.

Related calculators

Sources

Brzycki 1993 - Strength testing: predicting a one-rep max from reps-to-fatigue.
Mayhew et al. 1992 - Relative muscular endurance performance as a predictor of bench press strength.
LeSuer et al. 1997 - The accuracy of prediction equations for estimating 1-RM performance.