UnitConv

One Rep Max (1RM) Calculator

Estimate your one-rep max from any set with six proven formulas

Your Estimated 1RM
116.7
kg
Representative value (Epley)
Epley
116.7
kg
Brzycki
112.5
kg
Lander
113.7
kg
Lombardi
117.5
kg
Mayhew
119.0
kg
O'Conner
112.5
kg

Average of all formulas: 115.3 kg

Compare Formulas

Epley116.7 kg
Brzycki112.5 kg
Lander113.7 kg
Lombardi117.5 kg
Mayhew119.0 kg
O'Conner112.5 kg

Percentage of 1RM Training Table

Suggested loads for each rep range based on your estimated 1RM.

1 reps
116.7 kg
100%
2 reps
110.8 kg
95%
3 reps
108.5 kg
93%
4 reps
105.0 kg
90%
5 reps
101.5 kg
87%
6 reps
99.2 kg
85%
7 reps
96.8 kg
83%
8 reps
91.0 kg
78%
9 reps
88.7 kg
76%
10 reps
87.5 kg
75%
11 reps
84.0 kg
72%
12 reps
81.7 kg
70%

Formulas Used

Epley: 1RM = weight x (1 + reps / 30)

Brzycki: 1RM = weight x 36 / (37 - reps)

Lander: 1RM = weight x 100 / (101.3 - 2.67123 x reps)

Lombardi: 1RM = weight x reps^0.10

Mayhew: 1RM = weight x 100 / (52.2 + 41.9 x e^(-0.055 x reps))

O'Conner: 1RM = weight x (1 + 0.025 x reps)

All formulas estimate your one-rep max from a sub-maximal lift. Epley is the most widely used; results agree best at low rep counts.

What is a One Rep Max Calculator?

A one-rep max (1RM) calculator estimates the maximum weight you could lift for a single repetition of an exercise, based on a set you performed with a lighter weight for several reps. Testing a true 1RM is risky and tiring, so lifters instead predict it from a sub-maximal set. This tool applies six established formulas - Epley, Brzycki, Lander, Lombardi, Mayhew and O'Conner - and shows a representative value (Epley) plus the average of all six. It also builds a percentage-of-1RM table so you can choose training loads for strength, hypertrophy or endurance. Works in kilograms or pounds.

How to Use

1. Choose kilograms or pounds. 2. Enter the weight you lifted and the number of clean repetitions you completed. 3. Read your estimated 1RM - the large number is the Epley result, with the other five formulas shown for comparison. 4. Use the percentage table to plan your training loads. Keep the rep count at 10 or below for the most accurate estimate.

Formula & Definition

Epley (representative): 1RM = weight x (1 + reps / 30) Brzycki: 1RM = weight x 36 / (37 - reps) Lander: 1RM = weight x 100 / (101.3 - 2.67123 x reps) Lombardi: 1RM = weight x reps^0.10 Mayhew: 1RM = weight x 100 / (52.2 + 41.9 x e^(-0.055 x reps)) O'Conner: 1RM = weight x (1 + 0.025 x reps) For example, lifting 100 kg for 5 reps gives an Epley 1RM of about 117 kg.

Interpreting Results

The estimated 1RM is most reliable when the set used roughly 2-10 reps; beyond about 10-12 reps the prediction increasingly overestimates true strength and the formulas diverge. Treat the number as a training reference rather than an exact figure, and re-test as you get stronger. The percentage table is handy for programming: heavy strength work sits around 85-100% of 1RM (1-5 reps), hypertrophy around 67-85% (6-12 reps), and muscular endurance below about 67% (15+ reps).

Frequently Asked Questions

What is a one-rep max (1RM)? ▾

Your one-rep max is the heaviest weight you can lift for a single repetition of an exercise with good form. It is the standard measure of maximal strength.

Which 1RM formula is most accurate? ▾

No single formula is best for everyone. Epley is the most widely used and reliable default; Brzycki tends to read slightly lower. All formulas agree most closely at low rep counts (about 2-5).

How many reps should I use for the estimate? ▾

Use a set of roughly 2 to 10 reps taken close to failure. Fewer reps give a more accurate estimate; sets above 10-12 reps make the prediction less reliable.

Is it safe to test my actual 1RM? ▾

A true 1RM test carries injury risk and should only be attempted with proper warm-up, technique and ideally a spotter. Estimating from a sub-maximal set is a safer everyday alternative.

How do I use the percentage table? ▾

Pick the load tied to your target rep range: about 85-100% of 1RM for strength, 67-85% for muscle growth, and below 67% for endurance. Adjust as you progress.

This tool provides an estimate for training reference only, not medical or coaching advice. Lift within your ability, warm up properly, and consult a qualified professional before attempting heavy or maximal loads.