1RM Calculator
Estimate your one rep max from any hard set of 1 to 12 reps, then see the weight for every percentage.
Use a set you took close to failure. The fewer the reps, the closer the estimate.
Enter the weight and reps of a recent set.
| % of 1RM | Weight | Reps, about |
|---|
How the 1RM calculator works
It uses the Epley formula, the same one NXTSTEP Fitness uses for the estimated 1RM on your new PBs:
1RM = weight × (1 + reps ÷ 30)
So 100 kg for 5 reps works out at 100 × (1 + 5 ÷ 30) = 116.7 kg.
The percentage table runs the same formula backwards, so the reps next to each weight are roughly what you could do for a hard set. Weights below 100% are rounded to the nearest 2.5 kg or 5 lb, the jumps most gyms can load.
What to do with your percentages
- 85-95% for 1-5 reps: heavy strength work on your main lift.
- 80-88% for 3-5 reps: the main lift in a powerbuilding day.
- 65-80% for 8-15 reps: muscle building sets and accessories.
- 40-60% for 3-5 reps: warm-up sets. The plate calculator works these out for you.
Estimates move as you get stronger, so plug in a fresh set every few weeks rather than reusing an old max.
Let the app do this for every set
NXTSTEP Fitness logs every set you do, flags a new PB the moment you hit one with your estimated 1RM, and charts each lift over time. With NXT Premium, Coach Titan reads those logs and sets your next target.
FAQ
How accurate is a 1RM calculator?
It's an estimate, but a good one when the set is heavy. Sets of 2 to 6 reps taken close to failure give the closest numbers. Above about 10 reps the estimate drifts, which is why this calculator stops at 12.
What formula does this 1RM calculator use?
The Epley formula: weight × (1 + reps ÷ 30). It's the same formula NXTSTEP Fitness uses for the estimated 1RM on your PBs.
Should I test my real 1RM?
You don't need to. A true max is useful before a powerlifting meet, but it's tiring and carries more risk. An estimate from a hard set of 3 to 5 reps is enough to plan your training. If you do test, warm up properly and use safety pins or a spotter.
How often should I recalculate my 1RM?
Every 4 to 8 weeks, or whenever your working sets start to feel easy. In the NXTSTEP Fitness app you see a fresh estimate every time you hit a new PB.