Percentage of 1RM Calculator Formula

Understand the math behind the percentage of 1rm calculator. Each variable explained with a worked example.

Use the Percentage of 1RM Calculator

Formulas Used

Target Weight

target_weight = round(one_rm * target_pct / 100 / 5) * 5

Estimated Max Reps

est_reps = round(30 * (1 - target_pct / 100) / (target_pct / 100))

95% 1RM

weight_95 = round(one_rm * 0.95 / 5) * 5

70% 1RM

weight_70 = round(one_rm * 0.70 / 5) * 5

Variables

VariableDescriptionDefault
one_rmYour 1RM(lbs)225
target_pctTarget Percentage(%)75

How It Works

How Percentage-Based Training Works

Formula

Working Weight = 1RM x Target Percentage

Rounded to the nearest 5 lbs for practical plate loading.

Common Percentages

  • 95%: Heavy singles/doubles (1-2 reps)
  • 85%: Strength work (3-5 reps)
  • 75%: Hypertrophy (8-10 reps)
  • 65%: Volume/endurance (12-15 reps)
  • 50%: Speed work or warm-up

    • Worked Example

    Your bench press 1RM is 225 lbs. You want to train at 75%.

    one_rm = 225target_pct = 75
    1. 01Target weight = 225 * 0.75 = 168.75 lbs
    2. 02Rounded to nearest 5 = 170 lbs
    3. 03Estimated max reps at 75% = 30 * (0.25) / 0.75 = 10 reps

    Frequently Asked Questions

    Why round to the nearest 5 lbs?

    Standard barbell plates come in 2.5, 5, 10, 25, 35, and 45 lb increments. The smallest increment per side is 2.5 lbs, making 5 lbs the minimum change.

    How often should I retest my 1RM?

    Every 8-12 weeks, or when your current weights feel significantly easier than expected. You can also use rep PRs to estimate a new 1RM.

    Are these percentages exact?

    They are guidelines. Individual variation means some people can do more or fewer reps at a given percentage. Use RPE alongside percentages for fine-tuning.

    Ready to run the numbers?

    Open Percentage of 1RM Calculator