One Rep Max Calculator
Your one rep max is the most you can lift for a single rep. The Epley formula estimates it from a set you can already do. Enter the weight and reps.
Calculate one rep max
Fill in the fields and select Calculate.
What you'll need
To use the one rep max calculator, have these figures ready:
- Weight lifted — for example, 100.
- Reps completed — for example, 5.
The calculator then returns the estimated one rep max the moment you press calculate.
How it works
One rep max = weight × (1 + reps ÷ 30)
You enter the weight lifted and reps completed, and the calculator returns the estimated one rep max using the formula above.
When to Use
Use the one rep max calculator to estimate the heaviest weight you can lift for a single repetition. Knowing your 1RM is essential for designing strength training programmes because most programmes prescribe weights as percentages of your 1RM. It is safer to estimate your 1RM from a submaximal lift using formulas like Epley or Brzycki rather than testing a true max, which carries injury risk.
What the result tells you
An estimated one rep max lets you set training weights as a percentage of your true maximum without the risk of testing a single heavy lift. The Epley estimate is accurate for sets of about ten reps or fewer and drifts higher on long sets, so use a heavier, lower rep set for the best figure to base your programme on.
Benchmarks & Interpretation
Here is how typical results are categorized and interpreted:
| Value / Range | Rating | Description |
|---|---|---|
| Bench press: 0.5x bodyweight | Beginner | Just starting strength training. |
| Bench press: 1.0x bodyweight | Intermediate | Solid progress after months of consistent training. |
| Bench press: 1.5x bodyweight | Advanced | Strong lifter with years of training experience. |
| Squat: 1.5x bodyweight | Intermediate | Good lower body strength. |
| Squat: 2.0x bodyweight | Advanced | Strong squatter, likely several years of training. |
Pro Tips & Advice
When estimating your 1RM, use a weight you can lift for 3-5 reps with good form — this gives the most accurate prediction. The Epley formula is the default here, but the Brzycki formula—1RM = weight × (37 / (37 - reps))—is a popular alternative that tends to estimate slightly lower. For sets of 10+ reps, both formulas become less reliable because local muscular endurance and conditioning begin to dictate performance more than absolute mechanical strength. Always use a spotter and warm up thoroughly when testing strength.
Step by step
- Enter the weight lifted (kg).
- Enter the reps completed.
- Select Calculate to read the estimated one rep max.
Worked example
Lifting 100 kg for 5 reps estimates a one rep max of 100 × (1 + 5 ÷ 30), about 116.7 kg.
Frequently asked questions
How is the one rep max worked out?
One rep max = weight × (1 + reps ÷ 30). Your one rep max is the most you can lift for a single rep. The Epley formula estimates it from a set you can already d…
How accurate is the estimate?
It is close for sets of about ten reps or fewer. Beyond that the estimate drifts, so use a lower rep set for the best result.
Which 1RM formula is most accurate?
The Epley and Brzycki formulas are most accurate for sets of 1-10 reps. For higher rep ranges (10+), accuracy decreases because muscular endurance becomes a bigger factor than pure strength.
Is testing a true 1RM dangerous?
Testing a true 1RM carries more injury risk than submaximal training. Always use a spotter, warm up thoroughly with progressive sets, and only attempt a true max if you have significant training experience. For most people, an estimated 1RM is sufficient for programming purposes.
How often should I re-test my 1RM?
Re-test every 8-12 weeks or at the start of a new training cycle. More frequent testing can be fatiguing and does not allow enough time for meaningful strength gains between tests.
How accurate is the One Rep Max Calculator?
This tool uses the Epley formula: 1RM = weight × (1 + reps/30). While Epley is the industry standard, the alternative Brzycki formula—1RM = weight × (37 / (37 - reps))—is also widely used. Epley tends to estimate slightly higher than Brzycki for sets above 5 reps. Note that both formulas are most accurate for sets of 10 reps or fewer; beyond that, muscular endurance factors reduce the reliability of the estimation. Double check your inputs, since a wrong number going in gives a wrong number coming out.
Is the One Rep Max Calculator free to use?
Yes. Every tool on GamersZone is free, with no account and no limit on how many times you calculate. The maths runs in your browser, so the numbers you enter are never sent to a server or stored.
How we calculate this
This tool uses the Epley formula: 1RM = weight × (1 + reps/30). While Epley is the industry standard, the alternative Brzycki formula—1RM = weight × (37 / (37 - reps))—is also widely used. Epley tends to estimate slightly higher than Brzycki for sets above 5 reps. Note that both formulas are most accurate for sets of 10 reps or fewer; beyond that, muscular endurance factors reduce the reliability of the estimation.