Is it safe to test my true 1RM?

With proper warm-up, good technique, and a spotter, a true 1RM test is relatively safe for experienced lifters. Beginners and intermediates are better served by formula estimates from a 3–5 rep set near failure.

What percentage of 1RM should I use for different goals?

Strength (1–5 reps): 85–100% 1RM. Hypertrophy/muscle building (6–12 reps): 65–85%. Muscular endurance (12+ reps): below 65%. These are guidelines — individual response varies.

Why do the Epley and Brzycki formulas give different results?

They use different mathematical models. Epley slightly overestimates at high rep counts; Brzycki is more conservative. Neither is universally more accurate — averaging them gives a reasonable estimate.

How do I use 1RM to program a strength training week?

Common templates: 5×5 at 80% 1RM, 3×3 at 90%, 1×1+ at 95% (testing). A linear progression model increases weight by 2.5 kg per session until you stall, then recalculates 1RM.

Formula Guide

How to Calculate Your One Rep Max (1RM)

Your one rep max (1RM) is the maximum weight you can lift for exactly one complete repetition with good form. It is the foundation of strength programming — training loads are expressed as percentages of 1RM (e.g. 80% for hypertrophy, 90%+ for strength). Since directly testing your 1RM risks injury, the Epley and Brzycki formulas estimate it from a submaximal set (e.g. 5 reps at 80% of your true max).

Last updated: March 31, 2026

The Formula

Epley:   1RM = weight × (1 + reps / 30)
Brzycki: 1RM = weight × 36 / (37 − reps)

Training weights from 1RM:
  Strength (1–5 reps):    85–100% of 1RM
  Hypertrophy (6–12 reps): 65–85% of 1RM
  Endurance (12+ reps):   < 65% of 1RM

Both formulas are most accurate for 1–10 rep ranges. Above 10 reps the estimate becomes less reliable. Use the average of both for a more robust estimate.

Variable Definitions

Symbol	Name	Description
weight	Load	The weight lifted in the test set, in kg or lbs
reps	Reps	The number of complete repetitions performed with that weight (use a weight where you reach near-failure)
1RM	One Rep Max	Estimated maximum weight you can lift for one repetition

Step-by-Step Example

A lifter bench presses 100 kg for 6 reps (near failure). Estimate their 1RM using both formulas.

Given

Weight:100 kgReps:6

Solution

1
Epley formula: 1RM = 100 × (1 + 6/30) = 100 × 1.2 = 120 kg
2
Brzycki formula: 1RM = 100 × 36 / (37−6) = 100 × 36/31 = 116.1 kg
3
Average estimate: (120 + 116.1) / 2 = 118 kg
4
80% training load (hypertrophy): 118 × 0.80 = 94.4 kg → use 95 kg
5
90% training load (strength): 118 × 0.90 = 106.2 kg → use 105 kg

Estimated 1RM ≈ 118 kg. Use 95 kg for hypertrophy work, 105 kg for strength sets.

Ready to calculate?

Use the free One Rep Max Calculator — instant results, no sign-up.

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Common Mistakes to Avoid

Using reps that are too many — formulas are reliable up to 10 reps; a 20-rep max estimate will be significantly off.

Using a weight where you have more left in the tank — the estimate assumes near-failure reps; leave only 1–2 reps in reserve.

Treating 1RM estimates as exact — they are 5–10% estimates. Test conservatively when loading near the calculated 1RM.

Forgetting to reset 1RM regularly — strength increases over time; recalculate your 1RM every 4–8 weeks for accurate programming.

Frequently Asked Questions

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