How accurate is a 1RM calculator?

When calculating from 5 reps or fewer, it is generally very accurate (within 5% of your true max). Accuracy drops significantly if you calculate from sets of 10+ reps because muscular endurance factors begin to skew the results.

Should beginners test their 1RM?

No. Beginners are better off using a 1RM calculator. Testing a true 1RM requires excellent technique under maximum load. Beginners have not ingrained the motor patterns enough to do this safely.

Which formula is best?

The Epley and Brzycki formulas are the industry standard. Epley tends to be slightly more accurate for sets over 5 reps, while Brzycki is very precise for low rep sets. Our calculator averages these or provides the most relevant output based on your rep input.

How often should I recalculate my 1RM?

You should recalculate at the end of a training block or whenever you hit a new rep PR (personal record). If your 5-rep max goes up, your estimated 1RM has gone up.

1RM Calculator

Stop guessing your strength. Accurately estimate your one rep max and generate exact percentage breakdowns for your working sets.

RTS Method

Science-Backed

Instant Results

Plate Rounding

How it works

Follow the exact steps to get your result instantly and privately.

Step 1

Step 1: Enter weight lifted

Input the exact amount of weight you lifted during your toughest set.

The Math: Predicting Maximal Strength

Our 1RM calculator utilizes established mathematical formulas to estimate your maximal strength. The most popular equations are the Epley formula and the Brzycki formula. The Epley formula is often preferred for higher rep ranges, while the Brzycki formula is highly accurate for fewer than 10 reps. Both formulas extrapolate the exponential relationship between weight and reps to failure.

RPE Intensity Meter

Interactive

Tap or hover any level below

Calculation Formulas

Epley Formula: 1RM = Weight × (1 + (0.0333 × Reps))
Brzycki Formula: 1RM = Weight × (36 / (37 - Reps))

Worked Example

If you squatted 225 lbs for 5 reps, the Epley formula calculation is 225 × (1 + (0.0333 × 5)). This evaluates to 225 × 1.1665, giving an estimated 1RM of 262 lbs.

Worked examples

Sample scenarios and their calculated results
Scenario	Calculation	Result
Lifter A — Bench Press	225 lbs × 5 reps	e1RM ≈ 262.5 lbs
Lifter B — Squat	315 lbs × 3 reps	e1RM ≈ 346.5 lbs
Lifter C — Deadlift	405 lbs × 8 reps	e1RM ≈ 512.9 lbs

Conversion reference

Standard percentage of 1RM to Reps table. Shows how many reps you can typically perform at a given percentage of your true max.
Percentage of 1RM	Expected Reps
100%	1 Rep
95%	2 Reps
93%	3 Reps
90%	4 Reps
87%	5 Reps
85%	6 Reps
80%	8 Reps
75%	10 Reps
70%	12 Reps
65%	15 Reps

DID YOU KNOW?

Quick facts

Estimates are most accurate when you use a set of 1 to 5 repetitions. The higher the reps, the less accurate the 1RM prediction becomes.
A true 1RM test is physically exhausting and can disrupt training for days. Using a calculator allows you to gauge progress without maxing out.
Different lifts have different rep-max profiles. You might be able to do more reps at 85% of your squat max compared to your deadlift max.