Free One Rep Max Calculator
Estimate your 1RM and training percentages.
What is the One Rep Max Calculator?
Your one-rep max — the most you can lift for a single rep — is the reference point most strength programs are built around. But actually testing a true 1RM is risky and tiring, so lifters estimate it from a set they've already done.
This calculator estimates your 1RM from a weight and rep count, and gives a percentage table so you can plan your working sets.
Last updated: Aug 12, 2026
What does this tool do?
You enter a weight and how many reps you completed with it, and the tool estimates the single-rep maximum using an established strength formula.
It then builds a table of common training percentages of that max, so you know what to load for different rep ranges and intensities.
Key features
1RM estimate
From any set of 1–20 reps.
Percentage table
Working weights at 60–100% of your max.
No max testing
Estimate safely from a normal set.
Instant
Results update as you type.
Private
Your numbers are calculated in the browser.
Example
Common use cases
- Lifters — Set training loads from a known max.
- Coaches — Prescribe percentages for clients.
- Powerlifters — Plan attempts and peaking cycles.
- Beginners — Understand how program percentages work.
- CrossFitters — Estimate maxes for workouts.
- Personal trainers — Program safely without max testing.
- Athletes — Track strength progress over time.
- Home gym users — Plan sessions without a spotter for maxes.
Benefits
- It avoids the risk of true max testing.
- The percentage table turns the max into a plan.
- It works from a set you'd do anyway.
- Your numbers stay on your device.
Tips
- Estimates are most accurate from sets of about 3–8 reps.
- Higher rep counts make the estimate less reliable.
- Use a weight you lifted with good form to failure or near it.
- Re-estimate as you get stronger to keep percentages current.
- Warm up thoroughly before heavy attempts.
- Use a spotter or safeties for anything near your max.
- Different formulas vary slightly — treat the number as a guide.
- Fatigue and form affect real performance on the day.
Common mistakes to avoid
Estimating from very high reps
Fix: Use sets of roughly 3–8 reps for a reliable 1RM estimate.
Treating the estimate as guaranteed
Fix: It's a planning figure; test cautiously with a spotter if you need a true max.
Using a set with poor form
Fix: Estimate from a clean, near-max set for accuracy.
Never updating it
Fix: Re-estimate as you progress so your percentages stay right.
How it works
- 1
Enter a lift
The weight and reps you completed.
- 2
See your max
Estimated 1RM plus a percentage table.
Frequently asked questions
From the weight and reps you lifted, using a well-established strength formula. It's an estimate, not a guarantee.
Programs prescribe loads as a percentage of your 1RM; the table gives you those working weights.
From the weight and reps you lifted, using a well-established strength formula. It's an estimate, not a guarantee.
Programs prescribe loads as a percentage of your 1RM; the table gives you those working weights.
Sets of about 3–8 reps give the most reliable estimate; very high reps are less accurate.
Only with proper warm-up and a spotter or safeties. Estimating avoids the risk for most training purposes.
The Epley formula, a widely used strength estimate.
No. Everything is calculated in your browser.
Conclusion
Estimating your one-rep max lets you program intelligently without risky max attempts. Pair it with the other health and fitness calculators to round out your training plan.