How to estimate your max lift without testing it

Guide · Updated 2026-11-10

Why lifters estimate a one-rep max from a harder set, how the Epley and Brzycki formulas work, and how to turn the estimate into working weights for training.

Open the One-rep max Free, in your browser, nothing uploaded.

Strength programmes are often written as percentages: “three sets of five at 80%”. Eighty percent of what? Of your one-rep max, the most you could lift once with clean form. Finding that number by trying it is hard on the body and needs a spotter, so the one-rep max tool estimates it from a set you already did, then lists the weights for each percentage. It is for gym-goers, coaches writing plans and students learning about training. For the cardio side of a week, set your effort bands with heart rate zones, and if you are training to gain or lose weight, the calorie calculator gives a daily energy figure.

What it is

The more reps you can do with a weight, the further that weight is below your best single lift. Both formulas in the tool turn that idea into a line of maths. Here w is the weight lifted and r is the number of reps done close to failure.

• Epley: 1RM = w × (1 + r ÷ 30). Each rep adds one thirtieth of the weight.
• Brzycki: 1RM = w × 36 ÷ (37 − r). The gap between 37 and your reps shrinks as reps go up, so the estimate climbs faster on long sets.

For sets of about 2 to 10 reps the two land close together, and the tool shows their average as the main number. A single rep needs no estimate: both formulas give the weight itself.

The tool then works backwards for the table. Each row is a percentage of the average, from 100% down to 50% in steps of 5. The About reps column flips Epley around, reps ≈ 30 × (100 ÷ percent − 1), to suggest how many reps that weight allows. It is a rough guide, because real people tire in different ways.

How to use it

1. Type the Weight lifted and choose kg or lb. Changing the unit converts the number already in the box.
2. Type the Reps done in that set. Use a set you pushed close to failure; an easy set gives a low estimate.
3. Read the Epley, Brzycki and Average results. The line below repeats your set and both formulas.
4. Pick Round the table to: no rounding, or the nearest 1, 2.5 or 5, to match the plates in your gym.
5. Read the Percentage table to find your working weights.
6. Press Reset to return to the starting example.

A worked example

You bench press 60 kg for 8 hard reps.

• Epley: 60 × (1 + 8 ÷ 30) = 60 × 1.2667 = 76.0 kg
• Brzycki: 60 × 36 ÷ (37 − 8) = 2,160 ÷ 29 = 74.5 kg
• Average: (76.0 + 74.48) ÷ 2 = 75.2 kg

Your plan asks for sets at 75% and 85%. With rounding to the nearest 2.5 kg:

• 75%: 75.24 × 0.75 = 56.4 kg, rounded to 57.5 kg, about 10 reps.
• 85%: 75.24 × 0.85 = 64.0 kg, rounded to 65 kg, about 5 reps.

A handy check: the 80% row is 60.2 kg, rounded to 60 kg, with about 8 reps. That is the set you typed in, so the table agrees with itself.

The same lift in pounds: switch the unit to lb and the box shows 132.3 lb, since 60 ÷ 0.45359237 = 132.28.

Where it is used

• Strength plans: most published programmes give loads as percentages, so a 1RM estimate turns them into real numbers.
• Tracking progress: if the weight for 5 reps rises over a few weeks, the estimate rises too, without a risky max test.
• Coaching groups: a coach can set one plan in percentages and let each athlete fill in their own weights.
• Physical education and sport science: the formulas are a clear example of a model fitted to data, and of how accuracy drops outside the range it was built for.

Common mistakes

1. Using a long set. Above 12 reps the tool shows a warning, because endurance starts to matter more than strength. At 15 reps with 60 kg, Epley says 90.0 kg and Brzycki 98.2 kg, a gap of over 8 kg. Use a set of 3 to 10 reps.
2. Using an easy set. If you stopped with several reps left, the estimate comes out low. Count only sets close to failure, with good form.
3. Mixing exercises. A squat estimate says nothing about your deadlift. Work out each lift on its own.
4. Training at 100% every week. The top row is an estimate of your limit, not a training weight. Most work happens well below it.
5. Forgetting the rounding. If your gym has only 5 kg steps, choose that rounding, or the table will show weights you cannot load.

Questions people ask

Why do Epley and Brzycki give different numbers? They were fitted in different ways, and they bend differently as reps rise. Their average sits between the two.

Can I use it for machines or dumbbells? Yes, the maths is the same, but machines and dumbbells feel different from a barbell, so treat the table as a starting point.

Does it matter if I lift in pounds? No. Pick lb and every result and table row is shown in pounds.

Should I test my real max instead? That is your choice to make with a coach. A real test needs a warm-up, safety bars or a spotter, and rest afterwards.