One Rep Max Calculator
Enter the weight you lifted and how many reps you did. You get your estimated one rep max (1RM) from five formulas, a training percentage table and a plate-loading guide for the bar.
Compare all formulas
| Formula | Equation | 1RM |
|---|
Training percentages
| % of 1RM | Weight | Load (rounded) | Typical reps |
|---|
Tap a row to load it on the bar below. Rounded loads use 2.5 kg or 5 lb jumps.
Plate-loading helper
How to use the One Rep Max Calculator
- Pick kg or lb and enter the weight of a recent hard set.
- Enter the reps you completed with good form (1 to 12 reps gives the most reliable estimate).
- Press Calculate to see your estimated 1RM from each formula and the average.
- Use the percentage table to pick training weights. Tap any row to send that weight to the plate helper.
- Check the plate helper for the plates to put on each side of the bar.
One rep max formulas
Each formula turns a set of several reps into an estimated single-rep maximum. w is the weight lifted and r the number of reps.
| Formula | Equation | 100 kg × 5 reps |
|---|---|---|
| Epley (1985) | w × (1 + r ÷ 30) | 116.7 kg |
| Brzycki (1993) | w × 36 ÷ (37 − r) | 112.5 kg |
| Lombardi | w × r0.10 | 117.5 kg |
| O'Conner | w × (1 + 0.025 × r) | 112.5 kg |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) | 113.7 kg |
Worked example: 100 kg for 5 reps. Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg and Brzycki gives 100 × 36 ÷ 32 = 112.5 kg. The calculator's headline number is the average of the two: 114.6 kg. The formulas agree closely for sets of 2 to 6 reps and drift apart as reps increase, so a heavy set of 3 to 6 reps gives the most trustworthy estimate.
Percentage of 1RM and reps
This is the classic guide used by many strength programs. Individual results vary: trained lifters and lower-body lifts often allow a few more reps at the same percentage.
| % of 1RM | Typical reps | Training focus |
|---|---|---|
| 90–100% | 1–4 | Maximal strength, peaking |
| 80–90% | 4–8 | Strength |
| 65–80% | 8–15 | Muscle growth (hypertrophy) |
| 50–65% | 15–30 | Muscular endurance, warm-ups, technique |
Loading the bar
A standard Olympic bar weighs 20 kg (men's) or 15 kg (women's); a standard pound bar is 45 lb. To load 100 kg on a 20 kg bar, put 40 kg on each side: for example one 25 kg, one 10 kg and one 5 kg plate. Always load heaviest plates on first (closest to the collar) and use clips or collars to keep plates from sliding.
Estimates are for guidance only. Warm up properly, use a spotter or safety arms for heavy sets and stop a set when your technique breaks down.
Frequently asked questions
What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift once with good form for a given exercise. Many strength programs set training loads as a percentage of it.
How is 1RM calculated from reps?
Formulas estimate it from a submaximal set. Epley uses weight × (1 + reps ÷ 30). Brzycki uses weight × 36 ÷ (37 − reps). For example, 100 kg for 5 reps gives 116.7 kg with Epley and 112.5 kg with Brzycki.
Which 1RM formula is most accurate?
No single formula is best for everyone. Epley and Brzycki agree closely at low reps and are the most widely used. Accuracy drops above about 10 to 12 reps, so test with a heavier set of 3 to 6 reps for the best estimate.
Is it safe to test my true 1RM?
Maximal lifts carry more injury risk, especially for beginners. Estimating from a set of 3 to 6 reps is safer. If you do test a true max, warm up well, use a spotter or safety bars and stop if your form breaks down.
How do I use the percentage table?
Programs often prescribe sets such as 5 × 5 at 80% or triples at 90%. Find the percentage in the table to get the weight. The typical rep column shows roughly how many reps most lifters can do at that load.
How does the plate calculator work?
It subtracts the bar weight from your target, halves the rest for each side and fills it with the heaviest plates you have first. If the exact weight cannot be made, it shows the closest weight you can load.