How to Calculate Your One Rep Max

Last updated November 16, 2026

The quick way: use a 1RM calculator

The fastest way to calculate your one rep max is to type a recent set into the one rep max calculator at the top of this page. Enter the weight, the reps you completed and lb or kg, then select Calculate 1RM. You get your estimated max from seven formulas, a percentage table for training and a set of warm-up weights.

Want to understand where the number comes from, or check it with a pencil? Keep reading. The math is simple enough to do on your phone between sets.

Step 1: pick the right set

Every 1RM formula needs two numbers: the weight you lifted and the reps you completed. The quality of that set decides how good your estimate is.

• Use 2 to 10 reps. Sets of 3 to 6 reps usually give the closest estimate. Past 10 reps, the formulas start to disagree.
• Go close to failure. The set should end with no more than one or two reps left in the tank. If you stopped with five reps to spare, the estimate will come out too low.
• Count only good reps. Half reps, bounced reps and reps where a spotter helped don't count.
• Use the total weight. Include the bar. A standard Olympic barbell weighs 45 lb (20 kg).

Step 2: the Epley formula, with a 225 lb × 10 example

The Epley formula is the most common way to calculate a one rep max, and it is the default on RepMaxLab.

1RM = weight × (1 + reps ÷ 30)

In plain words: divide your reps by 30, add 1, and multiply by the weight. Say you bench 225 lb for 10 reps:

1. 10 ÷ 30 = 0.333
2. 1 + 0.333 = 1.333
3. 225 × 1.333 = 300 lb

Your estimated bench press max is 300 lb. A second example with a shorter set: 185 lb for 6 reps gives 185 × (1 + 6 ÷ 30) = 185 × 1.2 = 222 lb.

Step 3 (optional): the Brzycki formula, same 225 lb × 10 example

The Brzycki formula is the other formula most lifters know. It is a good second opinion.

1RM = weight × 36 ÷ (37 − reps)

For the same set of 225 lb for 10 reps:

1. 37 − 10 = 27
2. 225 × 36 = 8,100
3. 8,100 ÷ 27 = 300 lb

Both formulas give exactly 300 lb at 10 reps. On shorter sets Brzycki comes out a little lower. For 185 lb for 6 reps it gives 214.8 lb, about 7 lb under Epley. To see why, read Epley vs Brzycki.

A shortcut: multiply by a number from this table

If you don't want to do the division, multiply the weight by the number for your reps. These multipliers come straight from the two formulas above.

Example: 155 lb for 5 reps × 1.167 = about 181 lb with Epley, or × 1.125 = about 174 lb with Brzycki.

How to calculate your bench, squat and deadlift max

The method is the same for every barbell lift. Only the numbers change.

• Bench press: 185 lb for 5 reps. Epley: 185 × 1.167 = about 215.8 lb. Use the bench press max calculator for a bench-specific page.
• Squat: 275 lb for 5 reps. Epley: 275 × 1.167 = about 320.8 lb. Brzycki gives 309.4 lb. See the squat max calculator.
• Deadlift: 365 lb for 3 reps. Epley: 365 × 1.1 = 401.5 lb. Brzycki gives 386.5 lb. See the deadlift max calculator.

One note on the deadlift: many lifters find they can pull more for a single than the formulas predict from a set of reps, so treat a deadlift estimate as a floor rather than a ceiling.

Example in kilograms: 100 kg × 5

The formulas don't care about units. Work in kilograms and the answer comes out in kilograms.

• Epley: 100 × (1 + 5 ÷ 30) = 100 × 1.1667 = 116.7 kg
• Brzycki: 100 × 36 ÷ (37 − 5) = 3,600 ÷ 32 = 112.5 kg

A heavier example: 140 kg for 3 reps gives 140 × 1.1 = 154 kg with Epley. To switch units, 1 kg = 2.2046 lb, so 116.7 kg is about 257 lb.

What if you stopped before failure?

Formulas assume the set was close to all-out. If you had reps left, add them before you calculate. If you did 5 reps but could have done 7, calculate with 7. This is the idea behind RPE (rate of perceived exertion): an RPE 8 set means about two reps left. The calculator's More options menu does this for you, and the RPE calculator uses a full RPE chart instead of a formula.

Which formula should you use?

There is no single best formula for everyone. A practical approach:

• Use Epley as your everyday number. It is simple and widely used.
• Check Brzycki for sets under 10 reps if you want a more cautious number.
• If the two disagree and you can't decide, use the average of all seven formulas in the calculator.
• Most important: use the same formula every time, so you can compare your progress month to month.

How accurate is a calculated 1RM?

A calculated 1RM is an estimate, not a guarantee. It is usually close when the set is short and hard, and it gets rougher as reps go up. At 225 lb, the seven formulas on this site stay within about 18 lb of each other for sets of 3 to 8 reps, but the gap grows to 73 lb at 15 reps. Your true max on a given day also depends on sleep, practice with heavy singles and technique. For the full picture, read are 1RM calculators accurate?

If you need an exact number, for a meet or a test, you can work up to a real single. How to test your 1RM safely walks through a step-by-step protocol.

Use your number

Once you have your 1RM, most programs ask for a percentage of it, such as 5 sets of 5 at 80%. Multiply your max by the percentage: 80% of a 300 lb max is 300 × 0.8 = 240 lb. The one rep max percentage calculator and the printable one rep max chart do this for every percentage at once.