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🏋️ One Rep Max (1RM)
Your one-rep max (1RM) is the most weight you can lift for a single rep. Hitting a true 1RM is risky, so most lifters estimate it from a heavier set. Enter the weight and reps — we show estimates from 4 popular formulas plus a percentage table for programming training loads.
Examples
Estimated 1RM: ~115-118 kg (avg)Estimated 1RM: ~100-105 kgFrequently asked questions
How accurate are 1RM estimates?
Within ~5% of your true 1RM if the working set is 3-6 reps. Estimates from higher rep counts (10+) get less reliable.
Which formula is best?
Epley is the most popular and roughly average. Brzycki tends to give slightly lower estimates; Lombardi slightly higher. The "average" of all four is usually the safe number.
Should I actually test my 1RM?
Generally no — risk of injury outweighs the small accuracy gain. Use estimates for programming. Tested 1RM is mostly for powerlifting competitions.
What % of 1RM should I train at?
Strength: 80-95% × 1-5 reps. Hypertrophy: 65-80% × 8-12 reps. Endurance: 50-65% × 15+ reps. See the % table below for prescriptions.
About this tool
One Rep Max (1RM) runs entirely in your browser using standard Web APIs. No data is sent to any server. The source for this tool is in our public GitHub repository.
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Why this tool
vs typical free web-tool sites
| 1vw | Typical free site | |
|---|---|---|
| Price | Free | Free |
| Signup required | No | Often (for premium features) |
| Ads inside the tool | No | Yes (banner + video) |
| Data sent to server | No (browser-only) | Yes (inputs analyzed for ads) |
| Total tools | 96 | Often <20 or scattered across sites |
| Bookmarkable URL per tool | Yes | Mixed |
| Loads in under 1s | Yes (static) | Often slow (ad tracking) |
| Multilingual | EN / ES / PT / FR / DE | Usually EN only |
| Open source | Yes | No |