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One Rep Max Calculator

Epley and Brzycki 1RM with training percentages.

Improving fitnessStep 6 of 6

Best for: Use it to set working weights (e.g. 5\u00d75 at 80% of 1RM) without max-testing.

Complete guide
Why this result happened View assumptions
Country (units):

Input

How it's calculated & sources
The One Rep Max Calculator uses the standard formula for this calculation. It runs entirely in your browser, so your inputs are never uploaded. Figures are educational estimates, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.
Key assumptions
  • Epley/Brzycki estimate
  • Accuracy drops above ~10 reps

Educational estimate only — not medical advice. Consult a qualified healthcare professional for decisions about your health.

Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.

How it works

Epley: 1RM = weight × (1 + reps/30)

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

Example

80 kg × 5 reps → Epley 93.3 kg · Brzycki 90 kg.

Frequently asked questions

Are 1RM estimates accurate?+

Within ~5% for reps 1–10. Less accurate above 10 reps.

Should I test a true 1RM?+

Only with experience and a spotter. Estimators are safer for most lifters.

Continue your journey

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Daily carbs, protein and fat for any goal and split.

Complete guide

Quick answers

Short, sourced answers to the questions people (and AI assistants) ask most.

What is One Rep Max?
A one-rep-max (1RM) calculator estimates the most weight you could lift once for an exercise, from a lighter set you've done for several reps \u2014 safer than testing a true max.
Why does One Rep Max matter?
It feeds BMI, calorie, body-fat and dosing calculations.
How is One Rep Max calculated?
It uses a validated rep formula (Epley) that scales your weight up based on how many reps you completed. Formula: Epley: 1RM = weight \u00d7 (1 + reps \u00f7 30).
What are common one rep max mistakes?
Mixing units - entering pounds where kilograms are expected.
When should you use the One Rep Max Calculator?
Use it to set working weights (e.g. 5\u00d75 at 80% of 1RM) without max-testing.

What is the One Rep Max Calculator?

A one-rep-max (1RM) calculator estimates the most weight you could lift once for an exercise, from a lighter set you've done for several reps \u2014 safer than testing a true max.

How the One Rep Max Calculator works

It uses a validated rep formula (Epley) that scales your weight up based on how many reps you completed.

Epley: 1RM = weight \u00d7 (1 + reps \u00f7 30)
  • weight — Weight lifted
  • reps — Clean reps completed (best below ~10)

Understanding the inputs

What each value means, why it matters, and a typical range — so you can fill in the calculator with confidence.

Weight

Your body weight, entered in kilograms or pounds.

Why it matters:
It feeds BMI, calorie, body-fat and dosing calculations.
Typical range:
Varies by person; tools accept metric or imperial.
How it affects results:
  • Higher: Raises BMI and calorie needs.
  • Lower: Lowers BMI and calorie needs.

Common mistake: Mixing units - entering pounds where kilograms are expected.

What impacts results most

  1. 1.
    Weight lifted (High impact)The base for the 1RM estimate.
  2. 2.
    Reps performed (High impact)More reps imply a higher 1RM.

Key assumptions

  • Epley/Brzycki estimate
  • Accuracy drops above ~10 reps

Training load by % of 1RM

Strength85\u2013100% (1\u20135 reps)
Hypertrophy67\u201385% (6\u201312 reps)
Endurance< 67% (12+ reps)

Worked example

Inputs: Lifted 100 kg for 5 reps (Epley) Calculation: 1RM = weight × (1 + reps ÷ 30) Result: ≈ 116.7 kg What it means: Accuracy drops above ~10 reps; use it to set training percentages.

Related concepts

How One-Rep Max connects to the concepts around it.

Protein:
The daily protein needed to build or keep muscle.
Lean Body Mass:
Body weight excluding fat.

Fitness learning path

A sensible order to learn these concepts.

Body CompositionLean Body MassProteinOne-Rep Max

Reviewed sources & methodology

Methodology: Professional Estimate · Last reviewed June 2026.

Keywords: 1rm, strength, lifting.

This tool is for general information only and is not medical advice. Consult a qualified healthcare professional for decisions about your health.

Reviewed by the Free Tools Galaxy editorial team · Updated June 2026 · Calculated privately in your browser.

Frequently asked questions

Is the One Rep Max Calculator free to use?+

Yes. Every tool on Free Tools Galaxy is 100% free, runs in your browser and requires no signup.

How accurate is the One Rep Max Calculator?+

One Rep Max Calculator uses the standard one rep max formula in double-precision arithmetic, so the same inputs always produce the same result and you can verify any figure by hand. It is an educational estimate — real-world outcomes depend on your actual rates, rules and assumptions.

Do you store my inputs?+

No. The One Rep Max Calculator runs entirely in your browser. Nothing is uploaded or saved to a server.

Can I use the One Rep Max Calculator on mobile?+

Yes — the interface is fully responsive and works on phones, tablets and desktops.

What are common mistakes to avoid?+

The most frequent mistake is mixing units. Double-check your inputs use a single, consistent unit before clicking Calculate.

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Epley and Brzycki 1RM with training percentages.

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