# One-Rep Max (1RM) Calculator

Calculate your one-rep max (1RM) using Epley and Brzycki formulas. Get training load recommendations for strength, hypertrophy, and endurance goals.

## What this calculates

The one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. This calculator estimates your 1RM using proven formulas so you can plan your training without the risk of actually attempting a max lift.

## Inputs

- **Weight Lifted** (kg) — min 1, max 500
- **Repetitions Performed** — min 1, max 30 — Number of reps completed with good form (1-30)

## Outputs

- **Estimated 1RM (Epley)** — One-rep max using the Epley formula
- **Estimated 1RM (Brzycki)** — One-rep max using the Brzycki formula
- **Training Load Zones** — formatted as text — Recommended weights for different training goals
- **Percentage Chart** — formatted as text — Key percentages of your 1RM

## Details

The Epley formula (1RM = weight x (1 + reps/30)) and the Brzycki formula (1RM = weight x 36/(37 - reps)) are the two most widely used methods for estimating one-rep max. Both are most accurate when using sets of 10 or fewer repetitions. For higher rep ranges, accuracy decreases but the estimates remain useful for programming purposes.

Knowing your 1RM allows you to calculate training percentages for different goals. Strength training typically uses 80-95% of 1RM for 1-5 reps, hypertrophy training uses 65-80% for 6-12 reps, and muscular endurance training uses 50-65% for 15+ reps. These percentages provide a framework for progressive overload.

For safety, it is generally recommended to estimate your 1RM using submaximal loads rather than actually attempting a true one-rep max, especially for exercises like squats, deadlifts, and bench press. Always use a spotter or safety equipment when training near your maximal capacity.

## Frequently Asked Questions

**Q: Which 1RM formula is more accurate?**

A: The Epley and Brzycki formulas produce very similar results for rep ranges of 1-10. The Epley formula tends to estimate slightly higher at higher rep ranges. Neither formula is perfectly accurate for any individual, as 1RM depends on muscle fiber type distribution, training experience, and technique. Using the average of both formulas provides the best practical estimate.

**Q: How many reps should I use for the most accurate estimate?**

A: For the most accurate 1RM estimate, use a set of 3-5 reps with a challenging weight. The accuracy of all 1RM formulas decreases significantly when using more than 10 reps. Sets of 1-5 reps typically produce estimates within 5% of your actual 1RM, while sets of 10+ reps may be off by 10% or more.

**Q: Should I actually test my one-rep max?**

A: Testing a true 1RM carries injury risk and requires proper preparation. It is generally recommended for competitive powerlifters and Olympic weightlifters who need precise maxes for competition. For most recreational lifters, estimating 1RM from submaximal sets is safer and sufficiently accurate for programming purposes. If you do test, ensure proper warm-up, use a spotter, and work up gradually.

**Q: How often should I recalculate my 1RM?**

A: Recalculate your estimated 1RM every 4-6 weeks as your strength progresses. This ensures your training percentages remain appropriate for progressive overload. If you notice you can easily exceed the prescribed reps at a given percentage, your 1RM has likely increased and should be retested or re-estimated.

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Source: https://vastcalc.com/calculators/sports/one-rep-max
Category: Sports & Fitness
Last updated: 2026-04-21