One-rep max calculator.

How the 1RM calculator works

Your one-rep max is the most weight you can lift for a single rep with good form. Testing it directly is tiring and carries some risk, so most lifters estimate it from a heavier set of a few reps. This calculator uses three well-known formulas:

Worked example

You bench press 100 kg for 5 reps. Using Epley:

100 × (1 + 5 ÷ 30) = 100 × 1.167 ≈ 117 kg

Brzycki gives 100 × 36 ÷ 32 = 112.5 kg. The difference between formulas is a useful reminder that every estimate is approximate. Treat the number as a guide, not a guarantee.

How accurate are 1RM estimates?

Estimates are most reliable when:

• The set was heavy: roughly 2–8 reps. Above about 10 reps, predictions drift because endurance starts to matter as much as strength.
• The set was close to failure. If you stopped with reps left, your estimate will be low. Add your reps in reserve to the rep count, or see our RPE and RIR chart.
• Form was consistent. A paused bench and a touch-and-go bench aren't the same lift.
• You compare like with like. The trend in your estimated 1RM over time is more useful than any single number.

Using the percentage chart

Many programs prescribe weights as a percentage of your 1RM, for example "5 sets of 5 at 80%." Enter a recent set above and the chart fills in the working weights. The "≈ reps" column shows roughly how many reps each percentage allows, based on the Epley formula. Real-world numbers vary by lifter and exercise, so use it as a starting point and adjust by feel.

How to test your 1RM safely

1. Warm up thoroughly with ramp-up sets: bar × 10, ~50% × 5, ~70% × 3, ~80% × 1–2, ~90% × 1. See warm-up sets.
2. Use your estimated 1RM to choose your first attempt, around 95% of it.
3. Add small jumps of 1–5% per attempt, resting 3–5 minutes between them.
4. Stop when form breaks down or bar speed slows dramatically. That's your max for today.
5. Always use a spotter or safety arms for bench press and squat.

You don't have to test at all to make progress. Tracking your estimated 1RM from regular training sets shows whether your strength is moving, which is the whole point of progressive overload.