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One-rep max (1RM) calculator

Estimate your one-rep max from a weight lifted for several reps (Epley formula).

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Enter Weight lifted (kg), Repetitions and the One-rep max (1RM) calculator works out Estimated 1RM (kg) straight away. For instance, with Weight lifted (kg) = 80 and Repetitions = 5 it returns Estimated 1RM (kg) = 93.333.

How to use it

  1. Enter your values: Weight lifted (kg), Repetitions.
  2. Read the result instantly: Estimated 1RM (kg).

Frequently asked questions

How does the One-rep max (1RM) calculator work?

It takes Weight lifted (kg) and Repetitions and derives Estimated 1RM (kg) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Weight lifted (kg) and Repetitions. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Weight lifted (kg) = 80 and Repetitions = 5, the calculator returns Estimated 1RM (kg) = 93.333. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Weight lifted (kg) = 88 and Repetitions = 10 instead, Estimated 1RM (kg) goes from 93.333 to 117.333 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Weight lifted (kg) = 72 and Repetitions = 3, Estimated 1RM (kg) comes out at 79.2. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Programming a block: estimating a one-rep max without testing it, setting working loads as a percentage of it, and tracking whether volume is actually going up.

What is the most common mistake?

Estimating a one-rep max from a high-repetition set. The formulas hold to about five reps; beyond ten they drift badly, because endurance starts to dominate strength.

How accurate is it, and what are the limits?

For general guidance only — not medical advice.

What is the difference between the One-rep max (1RM) calculator and the Lift percentage of 1RM calculator?

This one returns Estimated 1RM (kg); the Lift percentage of 1RM calculator returns Weight to load (kg). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

VO₂ max calculator is the closest one after this: Estimate your VO₂ max from a 12-minute (Cooper) run test.

Further reading

All guides →
How-toHow to Estimate Your One-Rep Max (1RM)Your one-rep max is the most you can lift once. Here's how to estimate it safely from a lighter set, how accurate it is, and how to train with it.How-toHow to Train With Percentages of Your 1RMPercentage-based training scales every lift to your one-rep max. Learn the strength and hypertrophy zones and how to set your working weights.How-toHow to Calculate a Wilks Score to Compare Powerlifting TotalsUse the Wilks coefficient to compare powerlifting totals fairly across bodyweights, so a lighter and heavier lifter can be ranked.ExplainerWhat Is a Wilks Score?The Wilks score compares powerlifting totals fairly across body weights. Here's the problem it solves, how it works, what the numbers mean, and its newer rivals.ExplainerPower-to-Weight Ratio Explained (W/kg in Cycling)Watts per kilogram is the number that decides who climbs fastest. Learn how W/kg works, what it means for FTP and how to improve it.ComparisonOne-Rep Max Formulas Disagree, and the Disagreement Is the PointEpley, Brzycki, Lombardi, O'Conner and Wathan are five curves through the same data. They agree within a few pounds at low reps and disagree by a quarter at fifteen — which is exactly how you know when an estimate is worth having.