About StrengthCalc
StrengthCalc is an independent website offering free one rep max (1RM) calculators and plain-language guides for people who lift weights. Every result shows its working: the formulas used, the range between them and the limits of an estimate.
Why it exists
Most 1RM calculators show one number from one formula, with no hint of how uncertain it is.StrengthCalc shows all six common formulas side by side, explains where each reads high or low, and rounds training weights to loads you can actually put on a bar — never above the number you asked for.
Principles
- Transparent: every equation, rounding rule and limit is published in the methodology.
- Honest about uncertainty: estimates are labelled as estimates, with warnings where they become unreliable.
- Sourced: factual claims cite published research or recognised textbooks, and our own reasoning is labelled as such.
- Private by design: calculations run in your browser. There are no accounts and nothing you enter is sent to us.
- Free: no signup, no paywall.
Who runs it
Muhammad Khuzaima — Creator and editor
Muhammad Khuzaima is the creator and editor of StrengthCalc. He built the site to give lifters one rep max calculators that show their working: every formula is checked against its published source and covered by automated tests before it goes live. He is responsible for the site’s content and corrects any error readers report.
StrengthCalc is independent and does not give medical or individual coaching advice; where that matters, we point you to qualified professionals.
How the site is funded
StrengthCalc currently shows no advertising and earns no money. In future it may display advertising (such as Google AdSense) to cover its costs. If it does, ads will be clearly labelled, kept away from the calculators’ inputs and results, and will never influence how anything is calculated. The privacy policy will be updated before any ads appear.
Contact
Questions, corrections and suggestions are welcome: strengthcalc.team@outlook.com. See the contact page for details.