One Rep Max Calculator

How to use the one rep max calculator

Enter a weight you lifted and how many clean reps you completed with it, ideally finishing the set close to failure. The calculator estimates your one-repetition maximum (1RM) using the two most widely used prediction equations — Epley and Brzycki — and averages them. It then builds a table of training weights from 50% to 100% of your max, rounded to practical plate increments, along with the typical number of reps and training goal for each zone.

The 1RM formulas

Here w is the weight lifted and r is the number of reps. The two formulas give identical answers at 10 reps and very similar results between 2 and 10. Below that Epley runs slightly higher, and above it Brzycki climbs faster — which is one reason estimates become unreliable with high reps.

Worked example

You squat 100 kg for 5 reps. Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg. Brzycki gives 100 × 36 ÷ 32 = 112.5 kg. The average estimated max is about 114.6 kg, so your set of 100 kg was about 87% of your max. If your programme calls for 3 sets of 8 at 75%, you would load about 86 kg — rounded to 85 kg on the bar. In pounds, the same principle applies: 225 lb for 5 reps suggests a max of around 258 lb.

Why estimate instead of testing?

A true 1RM test is the gold standard, but it is fatiguing, carries a higher risk of injury and requires a careful warm-up and usually a spotter. For most lifters, an estimate from a hard set of 3–8 reps is accurate to within about 5% and can be done as part of normal training. It also lets you track strength progress every week without ever maxing out.

Using percentages to programme training

• 85–100% (1–6 reps): maximal strength and neural efficiency. Long rests of 3–5 minutes.
• 67–85% (6–12 reps): the classic hypertrophy (muscle-building) range, though research shows muscle can be built across a wide range of loads when sets are taken close to failure.
• 50–67% (12+ reps): muscular endurance, technique work and warm-ups.

Many popular programmes — 5/3/1, Texas Method and various powerlifting plans — prescribe work as a percentage of 1RM or of a "training max" set at about 90% of your estimated max. Recalculate every few weeks as you get stronger.

Accuracy and limitations

Prediction equations are most accurate for compound barbell lifts — squat, bench press and deadlift — in reasonably trained lifters, and with sets of 10 reps or fewer. They are less reliable for machines, isolation exercises and beginners, whose technique and nervous system are still adapting. Endurance-oriented athletes can often perform more reps at a given percentage than the table suggests, while very strong, explosive lifters may perform fewer. Treat the result as a smart starting point and adjust from how the weights feel.

Strength training supports muscle and bone health at every age. If you are building muscle, pair your programme with adequate protein — the protein calculator gives a daily target — and enough energy from the calorie calculator. To estimate the energy a lifting session burns, see the calories burned calculator.

These estimates are for general training guidance only. Warm up thoroughly and use spotters or safety bars when lifting heavy.