One Rep Max Calculator - Estimate Your 1RM & Rep Table

What this tool does

Enter the weight lifted and the reps to estimate your one-rep max (1RM) with four formulas, average them, and get a training-load table from 60% to 100%. For setting squat, bench and deadlift loads and working out percentage-based sets in a program.

How it is calculated

Instead of testing a true single, it estimates from a multi-rep set. With w = weight and r = reps, the four formulas below are averaged and each result is also shown. If you lifted one rep, no formula is used and that weight is your 1RM. From the average it builds a nine-row load table at 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65% and 60%, listing the rough reps for each percentage (1, 2, 4, 6, 8, 10, 12, 16, 20) and the load to one decimal place.

Epley: w × (1 + r ÷ 30)
Brzycki: w × 36 ÷ (37 − r)
Lombardi: w × r^0.1
O'Conner: w × (1 + 0.025 × r)
Example: 100 kg × 5 reps → 116.7 · 112.5 · 117.5 · 112.5 → average about 114.8 kg; the 80% row is about 91.8 kg

Things to know

Above 10 reps a warning appears because the error grows, and above 20 reps no estimate is made. Sets of 3 to 6 reps give the most accurate estimate.
The load table pairs 1RM percentages with typical reps (100% × 1, 90% × 4, 80% × 8, 70% × 12, 60% × 20 and so on). If a program says '80% × 5', use the 80% row.
Formulas fit lifts differently; lower-body lifts tend to allow more reps at a given weight, so the true 1RM can be lower than the estimate.
Test a real 1RM only with a full warm-up and a spotter. Programming from an estimate carries far less injury risk.
Enter a set taken close to failure. A set with two or three reps left in reserve makes the 1RM come out lower than it really is.
Table loads include decimals, so round to the nearest plate increment you have (typically 2.5 kg or 5 lb).
The unit box just labels the result as kg or lb. It does not convert the number you typed, so pick the unit your plates use.

Frequently asked questions

Why do the formulas disagree?

Each was fitted to different populations and lifts. Under 5 reps they agree within 2–3%; the spread widens as reps rise, which is why the average is used.

Why is there no result above 20 reps?

The formulas spread apart as reps rise, and Brzycki's denominator (37 − r) shrinks so its value shoots up (about 5.1 times the weight at 30 reps). So sets above 20 reps are not estimated and a message is shown instead. For comparison, 60 kg × 10 reps gives 80.0 · 80.0 · 75.5 · 75.0, an average of about 77.6 kg; sets of 10 reps or fewer work best.

Does switching kg and lb change the result?

No. The formulas work in ratios and the unit choice only changes the label after the number. The result comes out in the unit you entered; to convert, use 1 lb = 0.4536 kg yourself.

How do I tell whether my 1RM has improved?

Log the same lift at the same rep count and compare estimates. Going from 100 kg × 5 to 105 kg × 5 means the estimated 1RM rose about 5%.

Why show several formulas?

There is no single 1RM equation; each rests on slightly different assumptions. Some track better at low reps, others stay steadier at higher ones. Reading the spread across several is closer to reality than trusting one number.

How do I use the percentage table?

Broadly: 85%+ for low reps when training strength, 70–80% for moderate reps when training size, and around 60% for higher reps when training endurance. Exercises and individuals vary, so treat the table as a starting point.

These are estimates. True 1RM varies with condition, technique and lift; attempt maximal loads only with safety equipment and a spotter.

📚 Worth reading

🏋️A first month at the gym→ 🏋️Picking weight and reps for strength training→ 🥶Preventing frozen water pipes and what to do if they freeze→ ♻️Recycling items people often get wrong→

About Privacy Policy Terms Contact