Estimates from general formulas, not medical advice. Check with a doctor before big changes to diet or training.
This one rep max calculator estimates your 1RM, the most weight you could lift for a single repetition, from the weight and reps of a hard set. It uses the Epley, Brzycki and Lombardi formulas and builds a percentage chart from 50% to 100% for programming bench press, squat and deadlift without testing a true max.
How to use
- Pick a calculator in the tabs and choose metric or imperial units; the choice is remembered.
- Body fat: measure your neck below the larynx, your waist at the navel (men) or narrowest point (women) and hips at the widest point, then enter them. Or switch to From BMI.
- Ideal weight: enter height and sex. One-rep max: enter the weight and reps of a hard set. Calories: pick an activity and minutes. Water: weight and daily exercise. Steps: step count and your height or stride.
- Results update as you type. Tap any result to copy it.
- The US Navy method (Hodgdon and Beckett, 1984) is usually within 3–4 percentage points of a DEXA scan. The BMI method (Deurenberg, 1991) is rougher and overestimates fat in muscular people.
- Ideal weight formulas were made for drug dosing, not as health targets; the BMI range is a broader guide.
- 1RM: Epley = w × (1 + reps/30), Brzycki = w × 36 / (37 − reps), Lombardi = w × reps^0.10. All are most accurate for 2 to 10 reps.
- Calories use MET × weight (kg) × hours from the Compendium of Physical Activities and include your resting burn. Fitness trackers and machines may show different numbers.
- Water: about 35 ml per kg plus exercise. Food covers roughly 20% of water intake; EFSA suggests about 2.0 L a day for women and 2.5 L for men from all sources.
The formulas
Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). Lombardi: weight × reps^0.10. For 100 kg lifted 5 times, Epley gives 116.7 kg, Brzycki 112.5 kg and Lombardi 117.5 kg. The average is a sensible working estimate.
All three are most accurate between 2 and 10 reps. With more reps, endurance starts to matter and the estimates spread apart.
Using the percentage chart
Most strength programs prescribe loads as a percentage of 1RM: around 85–90% for sets of 3–5, 70–80% for sets of 8–12. The chart shows these loads for your estimate, so you can plan without a max-out session, which is safer, especially without a spotter.
Use sets taken close to failure with good form; an easy set underestimates your max. These are estimates from general formulas, not medical advice. Nothing you enter leaves your device.
Frequently asked questions
How do I calculate my one rep max?
Enter the weight and reps of a hard set, for example 80 kg for 6 reps. The calculator applies three formulas and shows the average, about 95 kg here.
Which 1RM formula is most accurate?
They perform similarly between 2 and 10 reps. Epley tends to read higher at higher reps and Brzycki lower; using the average evens this out.
Is it safe to test a true 1RM?
It can be with experience, a warm-up and a spotter or safety bars. Estimating from a 3–5 rep set gives a close number with less risk.
What percentage of 1RM should I train at?
Roughly 85–90% for strength sets of 3–5 reps, 70–80% for 8–12 reps and below 65% for endurance or technique work.
Does it work for any exercise?
It is most reliable for compound barbell lifts like squat, bench press and deadlift. Machines and small isolation exercises vary more.