One Rep Max Calculator – Estimate Your 1RM and Training Loads
1RM Calculator
Use this one rep max calculator to estimate your 1RM safely without testing it physically. Enter the weight you lifted and how many reps you performed.
Quick answer
A one rep max calculator estimates the heaviest weight you could lift for a single repetition (your 1RM) without having to test it. Enter the weight you lifted and how many clean reps you completed, optionally pick the exercise, and click Calculate 1RM. The tool averages the Brzycki and Epley formulas and shows training loads from 50% to 95% of your 1RM.
Our free one rep max calculator is designed for strength training in kilograms or pounds. It is safer than a true max attempt because you only need a set of 2 to 10 reps that you can complete with good form.
Estimates are most accurate for sets of 10 reps or fewer. Always warm up, use a spotter or safety bars on heavy lifts, and stop if form breaks down. Beginners and anyone with injuries or health conditions should get guidance from a qualified coach or doctor before heavy lifting.
How the One Rep Max Calculator Works
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
- Epley: 1RM = weight × (1 + reps ÷ 30)
- The one rep max calculator averages both results and rounds to the nearest 0.5.
Example: lifting 100 kg for 5 reps gives about 112.5 kg with Brzycki and 116.7 kg with Epley, so the estimated 1RM is about 114.5 kg.
Training Percentages Chart
| % of 1RM | Typical reps | Training goal |
|---|---|---|
| 90 to 95% | 1 to 3 | Maximum strength |
| 80 to 85% | 4 to 6 | Strength |
| 70 to 75% | 8 to 12 | Muscle growth (hypertrophy) |
| 60% | 12 to 15 | Muscular endurance and technique |
| 50% | 15+ | Warm-up and recovery |
How to Use the One Rep Max Calculator
Use the one rep max calculator in four steps.
Step 1: Enter the Weight Lifted and Reps Completed
Choose kg or lbs, then enter the weight you lifted and the number of full reps you completed with good form, for example 100 kg for 5 reps.
Step 2: Choose the Exercise (Optional)
Select Bench Press, Back Squat, Deadlift, Overhead Press or Other so you can keep track of which lift you calculated.
Step 3: Read Your Estimated One Rep Max
Click Calculate 1RM. The main card shows your estimated maximum for a single rep.
Step 4: Use the Training Percentages Chart
Below the result, see 95% down to 50% of your 1RM. Use these numbers to set the weights for your next training block.
Tips for Accurate 1RM Estimates
- Use a set of 3 to 6 reps for the best accuracy.
- Count only full reps with proper depth and lockout.
- Test when you are rested, not at the end of a hard session.
- Recalculate every 4 to 8 weeks as you get stronger.
Why Use a One Rep Max Calculator?
Many strength programmes are written as percentages of your 1RM, for example 5 sets of 5 at 80%. A one rep max calculator gives you that number without the fatigue and injury risk of a true max attempt, so you can train at the right intensity every session.
Frequently Asked Questions
Is this one rep max calculator free?
Yes. It is free with no sign-up.
How accurate is a 1RM calculator?
It is usually within a few percent for sets of 10 reps or fewer. Accuracy drops with very high reps.
Which formula is best?
Brzycki and Epley are both widely used; averaging them, as this calculator does, smooths out differences.
Should I test my true 1RM?
It is not required for most people. If you do, use a coach or spotter and proper warm-ups.
Can I use pounds?
Yes. Switch to Imperial (lbs) before calculating.
How often should I recalculate my 1RM?
Every 4 to 8 weeks, or after finishing a training block.