One Rep Max Calculator
Estimate your one-rep max from any set, across seven formulas, with a full training-weight table.
The set you did
Common rep counts
An estimate is not a licence to attempt the lift. Test a true max only with a warm-up progression, a spotter or safety bars, and enough training history behind you. Most people never need to.
This estimates your one-rep max from a weight and the number of reps you completed with it.
It shows several formulas side by side and gives training percentages based on the result.
What a one-rep max is
Your one-rep max is the heaviest weight you can lift once with good form. It is the reference point most strength programmes are written around, since loads are usually prescribed as a percentage of it.
Testing a true 1RM is taxing and carries real injury risk, so most lifters estimate it instead from a set they can actually complete. Lift 225 lb for 5 reps and the formulas put your max somewhere around 253-263 lb.
The estimate is reliable in a narrow band. Under about 5 reps it is close; past 10 it degrades quickly, because at high rep counts you are measuring endurance as much as strength, and that relationship varies enormously between people.
A 9.4 lb spread from the same set. The two formulas cross at 10 reps, where both give exactly 300 lb; below that Epley reads higher and above it Brzycki does.
What to enter
- Weight lifted
- The load on the bar for the set you are basing the estimate on.
- Repetitions completed
- With good form, taken close to failure. A set with two reps left in the tank underestimates your max.
- Formula
- Epley and Brzycki are the most common. They agree at 10 reps and diverge either side of it.
Training percentages of 1RM
- 90-100%
- 1-3 reps. Maximal strength work. High fatigue cost, used sparingly.
- 80-90%
- 3-6 reps. The main strength range for most programmes.
- 70-80%
- 6-12 reps. Hypertrophy territory, and where most volume lives.
- 50-70%
- 12+ reps. Endurance, technique work and warm-up sets.
What this assumes
The formulas assume the set was taken near failure with consistent form. A conservative set produces a conservative estimate.
1RM is lift-specific. A squat estimate says nothing useful about your bench, and technical lifts like the deadlift often estimate less reliably.
How to calculate your one-rep max
Take a set close to failure, then apply a formula to the weight and rep count.
- w
- Weight lifted
- reps
- Repetitions completed with good form
Warm up properly. Several ascending sets. A cold heavy set is both less accurate and more likely to injure you.
Pick a weight you can do for 3-6 reps. This is the range where the estimate is most reliable. Higher rep sets introduce more error.
Take the set close to failure with good form. Stop when form breaks down, not after. Reps with degraded technique inflate the estimate and risk injury.
Apply a formula and use it as a range. Different formulas give different answers. Treat the result as a band, and adjust based on how the prescribed loads actually feel.
See a worked example: the same set, two answers
- Set
- 225 lb for 5 reps
Epley: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5 lb.
Brzycki: 225 × 36 ÷ (37 − 5) = 225 × 1.125 = 253.1 lb.
So your max is somewhere around 253-263 lb. Use the lower figure when programming, since overestimating costs more than underestimating.
At 80% of a 260 lb max, working sets would be about 208 lb.
About 253-263 lb
Frequently asked questions
Good at low rep counts and progressively worse as reps rise. Under about 5 reps it is usually within a few percent; past 10 the error grows quickly.
The reason is that high-rep performance measures muscular endurance as much as maximal strength, and the relationship between the two varies a lot between individuals.
They were fitted to different data. Epley scales linearly with reps; Brzycki uses a slightly different curve.
They cross at 10 reps, where both give exactly the same answer. Below 10 Epley reads higher; above 10 Brzycki does. Neither is more correct in general.
Rarely, and only if you are experienced, well warmed up, and ideally have a spotter. Powerlifters test in the run-up to a competition; for most people it is not worth the risk or the fatigue.
An estimate from a 3-5 rep set gives you what you need for programming without a maximal attempt.
No. Each lift needs its own estimate, and the relationship between them varies a great deal by build and training history.
Technical lifts are also less consistent. Deadlift estimates in particular can be unreliable, because grip and lower-back endurance often limit high-rep sets before the prime movers do.
Every 4-8 weeks, or whenever prescribed loads start feeling clearly too easy. Strength changes fastest when you are new to training.
A stale 1RM makes a whole programme drift. If 80% feels like 70%, the estimate has fallen behind rather than the programme being wrong.
Depends on the goal. 80-90% for maximal strength, 70-80% for hypertrophy, and lighter loads for endurance and technique.
Most well-built programmes spend the bulk of their volume in the 70-85% band, with occasional heavier work rather than constant maximal effort.
Problems people actually run into
Estimating from a high-rep set
A 20-rep set tells you about muscular endurance, not maximal strength, and the formulas were never fitted for that range.
Use 3-6 reps. If you can only do a weight for 15, it is too light to estimate a max from reliably.
Counting reps where form broke down
The last two reps of a hard set often involve some drift in technique. Counting them inflates the estimate and makes every prescribed load slightly too heavy.
Count only reps you would be happy to be filmed doing. It produces a lower number and a programme that actually works.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 4, 2026