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One-Rep Max Calculator

Estimate your 1RM from any hard set — with the 65–95% training loads your program calls for

Your Lift

To clean failure — estimates are best under 10 reps

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Quick summary

Enter a weight and the number of clean reps you did, and this calculator estimates your one-rep max (1RM) by averaging two formulas: Epley (w × (1 + reps/30)) and Brzycki (w × 36/(37 − reps)). For example, 225 × 5 estimates a 1RM of about 258. The formulas agree exactly at 10 reps and drift apart as reps fall or rise. A load table then converts your 1RM into 65–95% working weights.

Reviewed by Simple Calculators TeamLast reviewed

For information only — not medical advice. Results are estimates from published formulas and can't account for your health history. Talk to a doctor or other qualified clinician before making health decisions.

How to use this calculator

  1. Pick a recent hard set done with good form, ideally 3–10 reps taken close to failure.
  2. Enter the Weight Lifted (lb or kg); results come back in the same unit you enter.
  3. Enter the Reps Completed, from 1 to 15. Count only full, clean reps.
  4. Read your estimated 1RM (the average of Epley and Brzycki), with each formula's estimate shown underneath.
  5. Use the Training Loads from Your 1RM table to pick working weights, for example about 85% for sets of 5–6 or 75% for sets of 9–10.

One-Rep Max Formulas

Epley Formula

1RM=w×(1+r30)1RM = w \times \left(1 + \frac{r}{30}\right)
w
Weight lifted (lb or kg)
r
Reps completed with good form (1–15); with 1 rep, 1RM = w

Worked example

225 lb lifted for 5 reps

Given
w = 225 lb
r = 5
Calculation
1RM=225×(1+530)=225×1.16671RM = 225 \times \left(1 + \frac{5}{30}\right) = 225 \times 1.1667
Result
Epley 1RM = 262.5 lb

Brzycki Formula

1RM=w×3637−r1RM = \frac{w \times 36}{37 - r}
w
Weight lifted (lb or kg)
r
Reps completed with good form (1–15); with 1 rep, 1RM = w

Worked example

225 lb lifted for 5 reps

Given
w = 225 lb
r = 5
Calculation
1RM=225×3637−5=810032=253.1251RM = \frac{225 \times 36}{37 - 5} = \frac{8100}{32} = 253.125
Result
Brzycki 1RM ≈ 253.1 lb

Estimated 1RM and Training Loads

1RMest=1RMEpley+1RMBrzycki2,Load=1RMest×p1001RM_{est} = \frac{1RM_{Epley} + 1RM_{Brzycki}}{2}, \quad \text{Load} = 1RM_{est} \times \frac{p}{100}
1RM_est
The average of the two estimates, shown as your estimated 1RM
p
Training percentage from the load table (65–95%)

Worked example

Same set of 225 lb × 5, working weight at 85%

Given
Epley = 262.5 lb
Brzycki = 253.125 lb
p = 85%
Calculation
1RMest=262.5+253.1252=257.8125;257.8125×0.85=219.141RM_{est} = \frac{262.5 + 253.125}{2} = 257.8125;\quad 257.8125 \times 0.85 = 219.14
Result
Estimated 1RM ≈ 257.8 lb; 85% load ≈ 219.1 lb

Frequently asked questions

How do I calculate my one-rep max without maxing out?

Take a recent hard set and apply an estimation formula instead of attempting a true max. For example, 225 lb for 5 clean reps gives 262.5 lb with Epley and about 253.1 lb with Brzycki; this calculator averages them to about 257.8 lb. Estimates from sets of roughly 3–10 reps tend to be the most useful, because accuracy falls off as reps climb.

How is one-rep max calculated?

This calculator works out two estimates and averages them. Epley multiplies the weight by 1 plus reps divided by 30; Brzycki multiplies the weight by 36 and divides by 37 minus reps. If you enter 1 rep, both formulas return the weight you lifted. The average is your estimated 1RM, and each training load is that number times its percentage, rounded to one decimal.

Which formula is more accurate, Epley or Brzycki?

Neither formula is clearly more accurate for everyone, which is why this calculator averages them. They give identical results at 10 reps. Below 10 reps Brzycki gives the lower estimate — about 4% lower at 5 reps (253.1 vs 262.5 for 225 × 5) — and above 10 reps Epley is lower. Differences between individual lifters and exercises are often larger than the gap between the formulas.

What percentage of my 1RM should I train at?

It depends on your goal: heavier percentages for strength, lighter ones for more reps. The table here pairs 95% with about 2 reps, 85% with 5–6, 75% with 9–10, and 65% with 13–15. As a general guide, around 85% and above suits low-rep strength work, roughly 65–85% suits muscle-building rep ranges, and lighter loads suit technique and endurance work.

Why does the calculator only accept up to 15 reps?

The calculator caps reps at 15 because rep-based formulas become much less reliable at high reps. With long sets, endurance and fatigue matter more than maximal strength, so two people with the same 1RM can do very different numbers of reps. For the most useful estimate, use a set of roughly 3 to 10 reps taken close to failure with good technique.

Should beginners test a true 1RM?

Generally no — an estimated max from a normal working set gives most of the useful information without the risk of a maximal attempt. If you do test, warm up progressively, use spotters or safety bars, and stop if your form breaks down. If you have an injury, a heart condition, or high blood pressure, check with a doctor before lifting near your maximum.

Key terms

1RM
One-rep max — the heaviest weight you can lift once with proper form.
Epley Formula
1RM = weight × (1 + reps ÷ 30) — the most common estimator.
Brzycki Formula
1RM = weight × 36 ÷ (37 − reps) — the standard alternative.
Training Percentage
A working weight expressed as % of 1RM — how strength programs prescribe loads.

Methodology, sources & limitations

This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.

For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.