One-rep max and training weight calculator
Enter a set you've completed and get an estimated 1RM plus the working weights for each training percentage.
Your training weights
This is an estimate, not a tested maximum. It's calculated from a single set, so it can't account for how your strength holds up across a session, your technique under a true maximal load, or how fresh you were. Treat these weights as a starting point and adjust from what you can actually complete.
How this is calculated · sources
Your estimated 1RM uses the Epley equation: weight × (1 + reps ÷ 30). Training weights are that estimate multiplied by each percentage, then rounded to the nearest 2.5 kg or 5 lb because that's the smallest jump most gyms can load. The repetition ranges shown beside each percentage are conventional guidance, not fixed values — how many reps you manage at a given percentage varies by person and by exercise.
- Accuracy of prediction equations for estimating 1RM performance LeSuer et al. (1997), Journal of Strength and Conditioning Research. Evaluates the Epley equation — estimated 1RM = weight × (1 + reps ÷ 30) — alongside six others. Predicted and actual 1RM correlated highly (r > 0.95), with accuracy best at lower repetitions and degrading as repetitions increase.
- Maximal repetitions at percentages of the one-repetition maximum Nuzzo, Pinto, Nosaka & Steele (2023), Sports Medicine. A meta-regression of ~7,000 people across 269 studies. Repetitions fall as %1RM rises, but the spread between individuals widens at lighter loads (about ±2.5 reps at 80% 1RM versus ±4.4 at 60%), and differs between exercises — so treat the rep ranges beside each percentage as typical, not exact.
Track this lift in BodyPlan
BodyPlan works out your e1RM from the sets you actually log — no manual entry. It tracks your personal records for every exercise, suggests your next working weight from your last session, and shows how each lift is trending over time.
- e1RM worked out automatically from your logged sets
- Personal records tracked per exercise
- Weight suggestions based on your last session
Free to download. No account needed to start.
How this 1RM calculator works
Your one-rep max is the heaviest weight you could lift once. Testing it directly is fatiguing and, with heavy compound lifts, carries real technique risk — so most lifters estimate it instead, from a set they've already done.
This uses the Epley formula: estimated 1RM = weight × (1 + reps ÷ 30). It's the same calculation BodyPlan runs on your logged sets to track estimated one-rep max records, so the number here matches what you'd see in the app for the same set.
Why rep count changes the accuracy
The relationship between reps and maximal strength holds up well at low rep counts and drifts as reps climb. A set of 3 tells you a lot about your maximum. A set of 15 tells you more about your muscular endurance and work capacity, so the estimate from it tends to read high.
For the most useful number, estimate from a set of 3 to 8 reps taken close to — but not to — failure.
Using training percentages
Percentages of 1RM are how strength programmes prescribe intensity. Roughly:
- 60–70% — higher-rep work, technique practice and volume accumulation.
- 70–80% — the main hypertrophy range for most people.
- 80–90% — strength work, where reps drop and load carries the stimulus.
- 90%+ — heavy singles and doubles. Effective, but fatiguing enough that most programmes use it sparingly.
These are guidelines rather than rules. How many reps you can do at a given percentage varies between people and between exercises — most lifters manage more reps at 80% on a leg press than on a deadlift.
Frequently asked questions
How accurate is a 1RM calculator?
It's an estimate, and it's most accurate from sets of about 1–5 reps. Above roughly 10 reps, fatigue and conditioning affect the result more than maximal strength does, and the estimate drifts high.
Which 1RM formula does this use?
The Epley formula — estimated 1RM = weight × (1 + reps ÷ 30). It's the same calculation BodyPlan applies to your logged sets when tracking e1RM records.
Should I actually test my one-rep max?
You don't need to. Estimating from a hard set of 3–5 reps gives you what you need to set training weights, without the fatigue and technique risk of a true maximal attempt.
What percentage of my 1RM should I train at?
Broadly: 65–75% for higher-rep hypertrophy work, 75–85% for the strength and hypertrophy overlap, and 85%+ for low-rep strength work. Most productive training sits in the middle of that range.
Lifting near your maximum carries injury risk. Warm up properly, use a spotter or safety pins on heavy compound lifts, and stop a set if your technique breaks down.