3RM (3-Rep Max) Calculator

By: Patrick Myers Patrick Myers is the CEO and Founder of Calculator Academy. He has over eight years of experience developing online calculators and holds a B.S. in Mechanical Engineering. His work focuses on formula implementation, calculator accuracy, unit conversions, and creating practical tools that are easy to use.

Last Updated: June 18, 2026

Calculate your 3-rep max, estimated max lift, weight lifted, or reps from any three values, with both pounds and kilograms supported.

3 Rep Max Calculator

Enter 3 values (leave exactly 1 field blank) to calculate the missing value.

Safety note: This calculator provides an estimate only. Use proper form, warm up, and use a spotter/safeties for heavy barbell lifts. Do not attempt a new max based only on this number. If you’re new to lifting, injured, pregnant, have cardiovascular risk, or have been advised to avoid heavy exertion, consult a qualified coach or clinician.

3 Rep Max Formula

The calculator estimates a 3 rep max from a lifted weight and reps using an estimated max lift as the middle step. It accepts pounds or kilograms and converts between units as needed.

E = W * (1 + 0.03 * (R - 1))
3RM = E * 0.93
W = E / (1 + 0.03 * (R - 1))
R = ((E / W - 1) / 0.03) + 1
  • 3RM = estimated 3 rep max
  • E = estimated max lift of the exercise
  • W = weight lifted
  • R = number of reps performed, from 1 to 12

If you leave 3RM blank, the calculator estimates your max lift from the weight and reps, then multiplies that estimate by 0.93.

If you leave Estimated Max Lift blank, it uses the lifted weight and reps to estimate the max lift.

If you leave Weight Lifted blank, it solves for the weight using the estimated max lift and reps.

If you leave Reps blank, it solves for the implied rep count using the weight lifted and estimated max, then rounds to a whole number. The rep value must be between 1 and 12.

Rep Multipliers for Estimated Max

These multipliers show how the calculator scales a set to estimate max lift before estimating 3RM.

Reps Estimated max multiplier Formula step
11.00W * 1.00
21.03W * 1.03
31.06W * 1.06
51.12W * 1.12
81.21W * 1.21
101.27W * 1.27
121.33W * 1.33

Common Training Percentages Near a 3RM

Value Approximate percent of estimated max Typical use
1RM 100% Maximum single rep estimate
3RM 93% Heavy triples and strength testing
5RM range About 87% to 90% Heavy working sets
8RM to 10RM range About 75% to 83% Moderate strength and hypertrophy work

Example Problems

Example 1: Estimate 3RM from weight and reps

You lift 200 lb for 6 reps.

E = 200 * (1 + 0.03 * (6 - 1)) = 230
3RM = 230 * 0.93 = 213.90 lb

Your estimated 3 rep max is 213.90 lb.

Example 2: Find weight lifted from estimated max and reps

Your estimated max is 150 kg, and the set was 4 reps. Leave Weight Lifted blank.

W = 150 / (1 + 0.03 * (4 - 1))
W = 150 / 1.09 = 137.61 kg

The weight lifted is 137.61 kg.

FAQ

Is a 3 rep max the same as 93% of a 1 rep max?

In this calculator, yes. The estimated 3RM is calculated as 93% of the estimated max lift. Real performance can vary depending on the lift, technique, fatigue, rest time, and how close the set was to failure.

Why does the calculator only allow 1 to 12 reps?

Rep-max estimates become less reliable as reps get higher. A set of 3 to 8 reps usually gives a more useful strength estimate than a high-rep set. The calculator limits reps to 1 through 12 to keep the estimate in a reasonable range.

Should you use pounds or kilograms?

You can use either unit. The result will be returned in the unit selected for the blank field. For example, if you enter weight in pounds but select kilograms for 3RM, the calculated 3RM will be shown in kilograms.

3rm calculator