What this calculator does
Every input on this 1rm calculator maps to a real decision, so the output is something you can act on immediately, not a rough ballpark you'll have to double-check elsewhere.
Estimates one-rep max from a submaximal set.
How to use the 1RM Calculator
- Enter your values in the fields on the left.
- Results update automatically.
- Use the action buttons to copy, share or print.
The formula
Epley: 1RM = w × (1 + reps/30)
Worked example
100 kg × 8 = 126.7 kg 1RM.
Common mistakes
- Reps too high (>10) reduce accuracy
- Bad form
- Fatigued sets
When to use it
Use for percent-based programming.
Pro tips for the 1RM Calculator
- Copy the result to paste it directly into email, Notion, or a spreadsheet cell.
- Use Print / PDF to export a clean, ad-free summary you can share with a client or advisor.
- The chart updates live — drag values up and down to build intuition for how the formula behaves.
Frequently asked questions
›Best formula?
Epley or Brzycki — close.
›Reps to use?
3–6 for best estimate.
›Test true 1RM?
Occasional, with spotter.
›Percentages?
80% × 5, 90% × 3, etc.
›Beginner?
Skip 1RM, focus on form.
›Is the 1RM Calculator free to use?
Yes. Every calculator on CalcPilot, including the 1RM Calculator, is free with no sign-up, no watermark, and no export limit.
›Does the 1RM Calculator store the numbers I enter?
No. All math runs locally in your browser — nothing is sent to a server, and closing the tab discards the inputs unless you save them to favorites.
Embed this calculator
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<iframe src="https://calcpilot.tools/calculators/1rm-calculator?embed=1" width="100%" height="720" style="border:1px solid #e5e7eb;border-radius:12px;max-width:720px;" loading="lazy" title="1RM Calculator — CalcPilot"></iframe>Related calculators
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