1RM 計算ツール
The detailed guide below is currently available in English.
Two ways to predict a max
The Epley formula multiplies your set weight by one plus reps divided by 30; the Brzycki formula scales weight by 36 over 37 minus reps. Both estimate the load you could lift exactly once, and both are most accurate when built from low-rep, high-effort sets — at 5 reps they usually land within a couple of percent of each other, while 12-rep sets can disagree substantially. This calculator reports each and uses their average as the headline.
Training with percentages
Programs prescribe loads as a share of your one-rep max: heavy strength work sits around 85–95% for 2–4 reps, hypertrophy blocks around 70–85% for 6–12 reps, and speed or technique work lighter still. The table converts your estimated max into those loads. Recalculate every few weeks as strength changes, and warm up thoroughly before testing near-maximal weights. Strength numbers are personal data, not medical advice.
よくある質問
Which formula should I trust?
For sets of 1–6 reps they are nearly interchangeable. Epley tends to run slightly high and Brzycki slightly low at higher reps, so the average shown here is a fair compromise. Direct testing after a full warm-up remains the gold standard.
Can I use reps above 12?
Predictions from high-rep sets are unreliable because muscular endurance, not maximal strength, limits the set. If all you have is a long set, split it: use a heavier load for fewer reps, or estimate conservatively and adjust after training at that load.