Calculator Inputs
Example Data Table
Sample plan using a 100 kg one rep max and 2.5 kg rounding.
| Percentage | Exact Load (kg) | Rounded Load (kg) | Typical Use |
|---|---|---|---|
| 50% | 50.00 | 50.00 | Speed work and technique practice |
| 60% | 60.00 | 60.00 | Volume building |
| 70% | 70.00 | 70.00 | Moderate training sets |
| 80% | 80.00 | 80.00 | Strength emphasis |
| 90% | 90.00 | 90.00 | Heavy singles or doubles |
| 100% | 100.00 | 100.00 | True max reference |
Formula Used
The calculator first estimates or accepts your one rep max. It then multiplies that value by each target percentage. Loads are rounded to your selected plate increment.
Core Load Formula
Working Load = 1RM × (Percentage ÷ 100)This converts your maximum strength estimate into usable training loads.
Epley
1RM = Weight × (1 + Reps ÷ 30)Common for moderate repetitions and practical programming.
Brzycki
1RM = Weight × 36 ÷ (37 - Reps)Popular when repetition counts stay relatively low.
Lombardi
1RM = Weight × Reps^0.10Gives a smooth progression across broader repetition ranges.
O'Connor
1RM = Weight × (1 + Reps ÷ 40)Often gives slightly more conservative estimates.
Mayhew
1RM = (100 × Weight) ÷ (52.2 + 41.9 × e^(-0.055 × Reps))Useful for bench-style performance estimation.
Lander
1RM = (100 × Weight) ÷ (101.3 - 2.67123 × Reps)Another classic choice for strength planning.
Average Method
Average 1RM = Mean of all available formula outputsBalances differences between formulas for steadier planning.
How to Use This Calculator
- Choose whether to estimate your one rep max or enter it directly.
- Enter the lift name, weight unit, and your performance data.
- Pick a formula, training goal, and plate rounding increment.
- Set the percentage range and step size for your plan.
- Press Calculate to display results above the form.
- Review the table, goal zone highlights, and load chart.
- Use CSV or PDF export to save the current plan.
- Adjust values and recalculate when your training block changes.
Frequently Asked Questions
1. What does a rep max percentage calculator do?
It converts your one rep max into percentage-based training loads. This helps you plan warm-ups, volume work, strength sets, and heavy practice with more consistent loading.
2. Which formula should I use?
Average mode is a balanced starting point. Epley and Brzycki are common for general strength work, while conservative lifters may prefer O'Connor for steadier estimates.
3. Is a direct one rep max better than an estimate?
A direct test can be more specific when performed safely and with good technique. Estimates are useful when you want lower fatigue or do not want to test a true maximum.
4. Why is load rounding important?
Real gyms use fixed plate and dumbbell jumps. Rounding makes the calculated load practical, repeatable, and closer to what you can actually place on the bar.
5. Can I use kilograms and pounds?
Yes. Select your preferred unit before calculating. The formulas work the same way because the percentage relationship stays identical in both systems.
6. Are high-repetition estimates reliable?
They can be useful, but accuracy usually drops as repetitions rise. Lower rep sets often provide better one rep max estimates for strength-focused programming.
7. Which percentages fit common training goals?
Power work often uses lighter percentages, hypertrophy commonly sits in moderate ranges, and strength training usually emphasizes heavier percentages near the top end of the chart.
8. Should beginners test a true one rep max?
Beginners often do better with submaximal sets and estimated values. Good technique, steady progress, and safe exposure usually matter more than chasing an all-out maximum.