How the 1RM estimate works
Nobody can lift their true max every week, so coaches estimate it from a hard set of a few reps. The calculator averages the two most widely used formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Example: 225 lb for 5 reps. Epley gives 262.5 lb, Brzycki gives 253.1 lb, and the average is about 258 lb.
How accurate is it?
Estimates are best from sets of 1 to 10 reps taken close to failure. Past about 10 reps the formulas drift apart, and endurance starts to matter more than strength. Your result also depends on the lift: estimates tend to be closer for bench press and squat than for deadlift, where grip and technique play a bigger part.
Treat the number as a planning tool, not a promise. A true max on the day depends on sleep, warm-up, technique and nerve.
Reading the percentage chart
The chart shows the load for each percentage of your estimated max and roughly how many reps most people can do there:
| % of 1RM | Typical reps | Common use |
|---|---|---|
| 90–95% | 2–3 | Heavy singles and doubles |
| 85% | about 5 | Strength sets of 3–5 |
| 80% | about 7 | Classic 5 × 5 territory |
| 70–75% | 10–12 | Volume and hypertrophy work |
| 50–60% | 15+ | Warm-ups, technique, speed work |
Tap any load in the chart to see the plates for it. To plan the warm-up before a heavy set, use the warm-up calculator.
Questions
How accurate is a one-rep max calculator?
Within a few percent for most people when the set was 1–10 reps close to failure. It gets less reliable with higher reps and varies by lift and by person.
Which 1RM formula is best?
No single formula wins for everyone. Epley tends to read slightly higher and Brzycki slightly lower at moderate reps, so this calculator averages them.
Should I test my true one-rep max?
You don't have to. Most programs work fine from an estimated max. If you do test, warm up properly, use a spotter or safeties, and stop if technique breaks down.
What is 80% of my max used for?
80% is a common working weight for strength sets of around 5 reps, such as 5 × 5. Most people can do roughly 7–8 reps at 80% when fresh.