How the Calculation Works
This calculator averages the two most validated 1RM formulas. The Epley formula (weight × (1 + reps ÷ 30)) and the Brzycki formula (weight × 36 ÷ (37 − reps)) agree closely for low rep sets and bracket the likely true value at higher reps. Averaging them gives a reliable single number to program from.
What to Do With Your 1RM
Use the percentage table above to set your working weights. Training for strength? Work mostly at 80 to 90%. Training for muscle? Most of your sets belong at 65 to 80%. If you are following our 3 day full body plan or the dumbbell only plan, the calculator tells you what weight matches each prescribed rep range.
Recalculate every few weeks from a recent hard set. A rising estimated 1RM is the clearest sign your plan is working. If it has been flat for a month, something needs to change: load, volume, sleep, or food. An AI workout plan generator makes those adjustments for you automatically based on your logged sets.
Frequently Asked Questions
- How accurate is a 1RM calculator?
- Accurate to within roughly 5% for sets of 2 to 6 reps. Accuracy drops as reps increase, because fatigue and muscular endurance vary between people. For the best estimate, enter a recent hard set of 3 to 5 reps.
- Which formula does this calculator use?
- The average of the Epley and Brzycki formulas, the two most validated 1RM equations. Epley tends to estimate slightly higher and Brzycki slightly lower, so the average is a reliable middle ground.
- Should beginners test their actual 1RM?
- No. Maximal single lifts carry the highest injury risk and beginners gain nothing from them. Use an estimated 1RM from a submaximal set instead. It gives you the same programming numbers with none of the risk.
- How do I use my 1RM in training?
- Program your working weights as percentages of it. Strength work typically uses 80 to 90% for 2 to 5 reps, muscle building 65 to 80% for 6 to 12 reps. The percentage table below the calculator does this maths for you.