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One Rep Max Calculator

100% Free

Estimate your one-rep max (1RM) from any working set using six proven strength formulas, then get a full training-percentage table to program your lifts — instantly and in-browser.

6 Formulas
% Table
Instant
100% Client-Side

1. Your set

Unit

Informational estimate only — not coaching or medical advice. Strength formulas are most accurate at 1–10 reps. Always warm up, use a spotter, and lift within your ability.

2. Estimated 1RM

Estimated one-rep max
114.9 kg
Range across formulas: 112.5–117.46 kg
By formula
Epley116.67 kg
Brzycki112.5 kg
Lombardi117.46 kg
Lander113.71 kg
O'Conner112.5 kg
Wathan116.58 kg
Training percentages
% of 1RMWeight~Reps
100%114.9 kg1
95%109.16 kg2
90%103.41 kg4
85%97.67 kg6
80%91.92 kg8
75%86.18 kg10
70%80.43 kg12
65%74.69 kg16
60%68.94 kg20
50%57.45 kg30

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How to Use

  1. 1 Choose kg or lb
  2. 2 Enter the weight you lifted
  3. 3 Enter how many reps you completed (1–15)
  4. 4 Read your estimated one-rep max and the formula range
  5. 5 Use the percentage table to plan your working sets

Features

  • Six established 1RM formulas averaged into one estimate
  • Min–max range so you can see how much the formulas disagree
  • Full training-percentage table from 50% to 100% of 1RM
  • Typical reps shown at each percentage for programming
  • kg and lb units with sensible rounding
  • Save lifts, track trends, and build programs with Pro

Why it Matters

Programming strength work around percentages of your one-rep max is the standard way to train safely and progressively — but maxing out for a true 1RM is risky and tiring. Estimating it from a normal working set lets you set accurate training weights without the danger of a true max attempt.

★★★★★

Use Cases

Powerlifters

Set training percentages without a risky true max

Coaches & Trainers

Prescribe accurate working weights for clients

Program Building

Plan 5/3/1 or linear progressions from your 1RM

Gym Beginners

Find safe starting weights for each rep range

What this tool does

The One Rep Max Calculator estimates the most weight you could lift for a single repetition, based on a heavier-rep set you’ve already done. It averages six established strength formulas (Epley, Brzycki, Lander, Lombardi, O’Conner, Wathan), shows the range between them, and builds a training-percentage table so you can program your working weights.

How it works

Each formula maps “weight × reps” to an estimated single-rep maximum. Because they disagree slightly — especially at higher reps — the tool reports the average as the headline number and shows the min–max spread so you know how confident to be. The percentage table then multiplies that estimate by 50–100% with the typical reps at each load.

A note on accuracy and safety

This is an informational estimate, not coaching or medical advice. Strength formulas are most accurate at 1–10 reps. Heavy lifting carries injury risk: warm up, use a spotter, and stay within your ability.

Free vs Pro

The free calculator gives a single estimate and stores nothing. A proposed Pro upgrade would log your lifts, chart your estimated 1RM over time per exercise, and auto-generate percentage-based programs — while the estimator stays free.

Privacy

Everything runs locally in your browser. Nothing you enter is uploaded, logged, or stored.

Frequently Asked Questions

How accurate is an estimated one-rep max?
Estimates are most accurate when based on a hard set of 1–10 reps; beyond about 10 reps they drift because fatigue and endurance start to matter more than raw strength. Using several formulas and averaging them, as this tool does, gives a more reliable number than any single formula. Treat it as a close estimate, not an exact max.
Which 1RM formula is best?
There's no single winner — Epley and Brzycki are the most popular and agree closely at low reps, while Lander, Lombardi, O'Conner, and Wathan can diverge at higher reps. Averaging them smooths out each formula's bias, which is why we show the mean plus the range.
How do I use the percentage table?
Multiply your estimated 1RM by a percentage to set the weight for a given rep range — for example, 80% for sets of about 8, or 90% for heavy triples. The table does this for you and shows the typical reps at each percentage.
Can I track my max over time?
The free tool calculates a single estimate and stores nothing. A proposed Pro upgrade would log each lift, chart your estimated 1RM trend per exercise, and build percentage-based programs. The estimator itself stays free.
Is this medical or coaching advice?
No. It's an informational estimate only. Maxing and heavy lifting carry injury risk — warm up properly, use a spotter, and train within your ability. Consult a qualified coach or physician as needed.
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Want to understand the math?

Browse all guides →
One-Rep Max Explained
one rep max

One-Rep Max Explained: Formulas, Accuracy, and How to Train With It

What a one-rep max is, how estimation formulas work, why averaging them is more reliable, how to use training percentages, and how to lift safely without a true max attempt.

25 Jun 2026

5 min read

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