Training percentages
The formula
How it works
Your one-rep max is the most weight you could lift for a single repetition. Rather than risk a true max attempt, this calculator estimates it from a lighter set — enter the weight and how many reps you managed.
FAQ
Which formula does this use?
The Epley formula, one of the most widely used estimates. It is most accurate for sets of about 10 reps or fewer; beyond that, all 1RM formulas become rough guesses.
Why estimate instead of testing a real max?
A true one-rep max attempt is tiring and risky, especially without a spotter. Estimating from a submaximal set gives you a training number safely, and you can retest as you get stronger.
How does Epley compare to other formulas like Brzycki?
Different formulas — Epley, Brzycki, Lombardi and others — fit slightly different curves to real lifting data, so they can give results a few percent apart. They tend to agree closely at low rep counts and diverge more as reps increase.
How often should I retest my one-rep max?
Every few weeks to a couple of months is typical, or whenever a training block ends. Testing too often adds unnecessary fatigue, since the estimate already updates automatically as your submaximal lifts improve.
Does the formula work the same for every exercise?
It is most reliable for major barbell lifts like the squat, bench press and deadlift. Smaller, more technical or stabiliser-dependent movements tend to follow the rep-to-percentage curve less predictably.
Is training near my estimated 1RM safe?
Occasional heavy singles or doubles are generally fine with good form and a spotter, but most programmes keep everyday training below the estimated max and reserve true near-max attempts for testing days.
How do I use the percentage table for programming?
Pick the percentage that matches the intensity your programme calls for — for example 70% for higher-rep volume work or 90% for low-rep strength work — and use the corresponding weight from the table.
About the one-rep max calculator
This calculator estimates your one-rep max — the heaviest weight you could lift once — from a set you can already do. Knowing your one-rep max, or 1RM, matters because most strength programmes prescribe weights as a percentage of it. Testing a true max is hard on the body and needs a spotter, so lifters usually estimate it instead from a comfortable set of a few reps.
How to use it
Enter the weight you lifted and the number of clean repetitions you completed, then pick kilograms or pounds. The calculator returns your estimated one-rep max and a full percentage table for planning workouts. For example, lifting 100 kg for 5 reps estimates a 1RM of about 117 kg. Use fewer reps for a more accurate estimate — sets under about six reps work best, since the formula drifts on very high-rep sets.
The formula
This uses the Epley formula, , where is the weight lifted and is the number of reps. A single rep is simply your max, so the calculator returns the weight itself in that case; from two reps up, each extra rep adds another of the weight. Training percentages then come straight from the result — 80% of your 1RM is a typical weight for a set of eight.
Where it is used
Coaches and lifters use the one-rep max to set training loads in strength programmes like 5×5 or percentage-based plans, where every session is tied to a fraction of the max. Powerlifters use it to plan attempts on the platform, and physiotherapists use submaximal estimates to prescribe safe rehab loads. Fitness apps track it over time as a simple, single-number measure of whether your strength is going up.