1RM Calculator
Calculate your estimated 1RM and see working weights by percentage
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Изчисли ориентировъчния си 1RM и виж работни тежести по проценти
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Why trust us?
- Estimated calculations
- Formulas are publicly known
- Not medical advice
- See "How do we calculate?" section
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What does the 1RM calculator calculate?
The 1RM (One Rep Max) calculator is an online tool that estimates your maximum strength without performing an actual one-rep max test. The calculator shows your estimated 1RM based on weight and reps from your workouts, and displays working weights by percentage (50%, 60%, 70%, 80%, 90% of 1RM). The calculator uses proven formulas (Epley and Brzycki) to estimate your maximum strength. It's useful for anyone who wants to program their workouts based on percentages, track strength progress, or plan training without testing true 1RM (which can be risky). The calculator helps you make informed decisions about training loads and progression.
How to use the 1RM calculator?
The 1RM calculator helps you estimate your maximum strength without performing a one-rep max test. Enter the weight and reps from your last workout and the calculator will estimate your 1RM.
- Enter weight and reps: Enter the weight (kg) and number of reps from your last set.
- Select formula (optional): Choose Epley (conservative) or Brzycki (more aggressive).
- Calculate: Click "Calculate" to see your estimated 1RM.
- Review working weights: View weights for different percentages of 1RM (50%, 60%, 70%, 80%, 90%).
Formulas:
- Epley formula: More conservative, suitable for most cases - 1RM = weight × (1 + reps / 30)
- Brzycki formula: More aggressive, may give higher values - 1RM = weight / (1.0278 - 0.0278 × reps)
Example with specific numbers
Example: Bench press 100 kg for 5 reps
- Weight: 100 kg
- Reps: 5 reps
- Estimated 1RM (Epley): 100 × (1 + 5/30) = 116.7 kg
- Estimated 1RM (Brzycki): 100 / (1.0278 - 0.0278 × 5) = 112.4 kg
- Working weights (based on 115 kg 1RM):
- 90% = 103.5 kg
- 80% = 92 kg
- 70% = 80.5 kg
- 60% = 69 kg
Sources and notes
The calculator uses the Epley and Brzycki formulas, which are widely recognized methods for estimating 1RM based on submaximal loads. The Epley formula is more conservative and suitable for most people, while Brzycki may give slightly higher estimates. These formulas are estimates and actual 1RM may vary based on exercise, form, fatigue, and other factors. Working weights by percentage help you program workouts effectively - 70-80% of 1RM is ideal for strength and hypertrophy, 50-60% for technique and endurance. Always prioritize safety and proper form over maximum weight.
Last updated: January 13, 2026
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- Linear Periodization Calculator – Generate training programs
- TDEE Calculator – Calculate daily calorie needs
Често задавани въпроси
What is 1RM?
1RM (One Rep Max) is the maximum weight you can lift for one repetition with proper form.
Which formula should I use?
The Epley formula is more conservative and suitable for most people. Brzycki may give higher values.
How accurate are the calculations?
The calculations are estimates. Your actual 1RM may vary depending on form, recovery, and other factors.