1RM計算機
挙上重量と回数から最大挙上重量（1RM）を推定します
What is a one rep max (1RM) and how is it calculated?
A one rep max (1RM) is the maximum weight you can lift for a single repetition. It's estimated using formulas like Epley: 1RM = Weight × (1 + Reps/30). For example, if you bench press 80kg for 8 reps, your estimated 1RM is about 101kg. Use 1RM percentages to plan training loads for strength, hypertrophy, or endurance.
（精度のため1〜12回を推奨）
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Create Free Account1RMとは？
1RM（ワンレップマックス）は、正しいフォームで1回だけ挙げられる最大重量のことです。筋トレにおいて、自分の筋力レベルを把握したり、トレーニング強度を決めたりするのに重要な指標です。1RMがわかれば、筋力アップ・筋肥大・筋持久力など目的に合わせた重量設定ができるようになります。
計算式の種類
1RMを推定する計算式にはいくつか種類があります。Epley式（1RM = 重量 × (1 + 回数/30)）は6〜10回程度のセットに向いています。Brzycki式（1RM = 重量 × 36/(37-回数)）は低回数（1〜6回）でより正確です。Lander式はバランスの良い計算式です。どの式も10〜12回を超えると精度が落ちるため、3〜6回で限界がくる重量で計算するのがベストです。
1RMの活用法
1RMを基準にトレーニング強度を設定しましょう。最大筋力狙い（1〜5回）なら1RMの85〜100%、筋力+筋肥大（6〜8回）なら75〜85%、筋肥大（8〜12回）なら65〜75%、筋持久力（12〜15回以上）なら50〜65%が目安です。あくまで推定値なので、フォームを優先し、高重量時は必ず補助をつけてください。
Frequently Asked Questions
How accurate are 1RM calculators?
1RM calculators are most accurate when using 3-6 reps at a heavy weight. Accuracy decreases significantly above 10 reps. The Brzycki formula tends to be most accurate for low reps (1-6), while the Epley formula works better for moderate reps (6-10). For best results, test with a weight you can lift for 3-5 reps with proper form.
Should I actually attempt my calculated 1RM?
Only attempt a true 1RM if you have experience with heavy lifting, proper form, and a trained spotter. For most training purposes, using calculated percentages of your estimated 1RM is safer and equally effective for programming. Many successful strength programs never require true maximal attempts.
How often should I test or recalculate my 1RM?
Recalculate your estimated 1RM every 4-8 weeks as you progress. This aligns with typical training cycles and ensures your working weights stay appropriately challenging. You can simply input your latest heavy set into the calculator rather than attempting a true 1RM test.
What percentage of 1RM should I train at?
For maximum strength, train at 85-95% of 1RM for 1-5 reps. For strength and size, use 75-85% for 5-8 reps. For hypertrophy (muscle growth), use 65-75% for 8-12 reps. For muscular endurance, use 50-65% for 12-20 reps. Most people benefit from varying percentages across their training week.
Why do different formulas give different results?
Each formula was developed from different research populations and methodologies. The Epley, Brzycki, and Lander formulas all make slightly different mathematical assumptions about the relationship between weight and reps. The differences are usually small (within 5%) and all provide useful estimates for training purposes.