What is one rep max (1RM)?

One rep max (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise with good form. It is used to measure strength and to calculate training weights for different rep ranges.

How do I calculate my 1RM safely?

The safest way is to use a submaximal test: perform a set with good form at a challenging weight for 3–10 reps, then use a 1RM formula to estimate your maximum. Avoid actual 1RM testing without a spotter.

What percentage of 1RM should I train at?

Training zones: 85–100% of 1RM for maximal strength (1–5 reps), 67–85% for hypertrophy/muscle building (6–12 reps), 50–67% for muscular endurance (13+ reps). Most programs use 70–80%.

One Rep Max Calculator

Name: One Rep Max Calculator
Author: Miikka

Estimate your one rep max for any strength exercise. Enter the weight you lifted and the number of reps to calculate your 1RM and training weights.

By Miikka · CalcBrew · Updated Sep 16, 2026

Exercise

Weight: 175 lb

20 lb660 lb

Reps: 5

120

Formula

🏋️ Bench press — estimated 1RM

196.9 lb

175 lb × 5 reps (Brzycki)

Brzycki

196.9 lb

Epley

204.2 lb

Lander

199.0 lb

Lombardi

205.6 lb

Training weights 🏋️ Bench press

% 1RM	Weight (kg)	Reps (estimate)	Goal
100%	196.9 lb(195.0)	1	Max / competition
95%	187.0 lb(185.0)	1	Max / competition
90%	177.2 lb(175.0)	3	Strength
85%	167.3 lb(165.0)	5	Strength
80%	157.5 lb(160.0)	6	Hypertrophy (strength)
75%	147.7 lb(150.0)	8	Hypertrophy (strength)
70%	137.8 lb(140.0)	10	Hypertrophy (volume)
65%	128.0 lb(130.0)	12	Hypertrophy (volume)
60%	118.1 lb(120.0)	15	Endurance / warm-up
55%	108.3 lb(110.0)	20	Endurance / warm-up
50%	98.4 lb(100.0)	20	Endurance / warm-up

⚠️ The estimate is based on mathematical formulas — your actual max may differ. Do not test your 1RM maximum without a spotter. This calculator is intended for planning training weights, not predicting competition maxima.

The one rep max calculator estimates the heaviest weight you could lift once with clean form. Enter the weight you used and the number of reps, and you get an estimate of your maximum strength without attempting a risky all-out single.

How the calculator works and what it’s for▾

How the one rep max is calculated

The calculator uses established formulas that convert your completed reps into an estimated maximum. The more reps you perform, the lighter the weight is relative to your true single, and the tool adjusts for this automatically.

For example, if you bench press 80 kg for six reps, your estimated 1RM lands clearly above 80 kg. Accuracy is best when reps stay roughly between two and ten.

What you enter and what you get

You provide the weight lifted and the number of repetitions. In return you get an estimate of your max, and often a table of percentages for different rep ranges to help you plan training loads.

That way you know which weight corresponds to, say, 80 % of your maximum when programming your strength work.

Who it is for

The tool serves gym-goers, powerlifters and coaches who want to program training around maximal strength without constantly testing a true max.

It also helps beginners track progress safely over time.

Tips and common mistakes

The result is an estimate, not a precise measurement. Fatigue, technique and daily readiness all affect your real max, so use recent, clean sets as input.

Avoid entering very high rep counts, since an endurance-style set lowers the reliability of the estimate.

🔄 Reviewed June 2026

Frequently asked questions

Cite this calculator

APACalcBrew. (2026). One Rep Max Calculator. https://calcbrew.com/one-rep-max-calculator

MLA“One Rep Max Calculator.” CalcBrew, 2026, calcbrew.com/one-rep-max-calculator.

Link to https://calcbrew.com/one-rep-max-calculator. Results are estimates; cite the underlying formula or data source for academic work.

More in Fitness & Sports · All calculators