How the One-Rep Max Calculator Works
Your one-rep max (1RM) is the heaviest weight you can lift for a single clean rep. You don't need to test it to know it: a hard set of a few reps predicts it closely. This calculator estimates your 1RM, places it on a beginner-to-elite scale relative to your bodyweight, and turns it into training weights you can use this week.
The formulas
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lombardi: 1RM = weight × reps0.10
Epley tends to read a little high at higher reps and Brzycki a little low, so your headline estimate is the average of the two. Lombardi is shown for comparison. If you enter a single rep, that weight is your 1RM.
How the strength levels work
Each lift is compared with your bodyweight — a 100 kg squat means something different at 60 kg bodyweight than at 110 kg. The five levels are broad, rounded bodyweight multiples that reflect commonly cited coaching benchmarks:
- Beginner — the first few months of consistent training.
- Novice — about 6–12 months of regular lifting.
- Intermediate — a couple of years of structured training.
- Advanced — many years of focused strength work.
- Elite — competitive-level strength.
Two honest caveats: heavier lifters usually lift more in total but less relative to their bodyweight, and strength naturally changes with age. Use the levels to track your own progress, not to judge yourself against someone else.
Using your training-weight table
- Strength (85–95%) — 1–5 reps, longer rest. Use sparingly.
- Muscle growth (65–85%) — 6–12 reps, where most of your training should live. See reps and sets explained.
- Endurance (below 65%) — 12+ reps, short rest, great for technique and warm-ups.
To keep the numbers climbing, add a little weight or a rep when a set feels easy — the core idea in progressive overload — and log every session so you can see the trend. The 8-week strength log makes that simple. Just starting out? The 30-Day Strength Challenge builds a base at home before you chase a bigger max.
Frequently Asked Questions
How do you calculate a one-rep max without testing it?
Lift a weight for as many clean reps as you can — ideally between 2 and 10 — then put the weight and reps into a formula. The Epley formula is weight × (1 + reps ÷ 30); the Brzycki formula is weight × 36 ÷ (37 − reps). This calculator averages the two, which tends to be accurate within a few percent for sets of 10 reps or fewer.
How accurate are one-rep max calculators?
For sets of about 2 to 10 reps taken close to failure, estimates are usually within about 5% of a true max. Accuracy drops as reps go up, because muscular endurance varies a lot between people. Sets of more than 12 reps are not reliable for predicting a single-rep max, so the calculator caps input at 12.
What is a good bench press for my bodyweight?
As a rough guide, an intermediate male lifter benches around his bodyweight for one rep, and an intermediate female lifter around 0.65 times her bodyweight. Beginners often start near half those numbers. These ratios shift with bodyweight, age and training history, so treat them as a way to track your own progress rather than a pass or fail mark.
What percentage of my 1RM should I train with?
Roughly 85–95% of your 1RM for 1 to 5 reps builds maximal strength, 65–85% for 6 to 12 reps suits muscle growth, and below 65% for 12 or more reps builds muscular endurance. Most lifters do the bulk of their training in the 70–85% range and only occasionally go heavier.
Should beginners test their true one-rep max?
Usually not. A true max attempt carries more risk and teaches you little that an estimate won't. Beginners progress fastest by adding small amounts of weight to sets of 5 to 10 reps with good form. If you do test a max, warm up thoroughly, use safety bars or a spotter, and stop if your technique breaks down.
Disclaimer: Estimates and strength levels are general guides, not medical or coaching advice. Lift with good technique, use safety equipment or a spotter for heavy sets, and check with a doctor or physiotherapist before heavy lifting if you have an injury, a heart condition or other health concerns.