Quick start
- Open the One Rep Max Calculator.
- Enter the weight lifted and the number of completed reps.
- Use the first example, "Bench example: 100 kg x 5", if you want to see a filled-out calculation before entering your own values.
- Calculate, read the formula line, then copy the result only after the units and assumptions look right.
Best uses
Use this guide when one of these tasks matches what you are trying to do.
- Estimate a one-rep max without testing a true max.
- Compare Epley and Brzycki estimates.
- Plan training percentages from a recent rep set.
- Track strength changes over time.
What this calculator is for
The One Rep Max Calculator estimates strength from a weight you lifted for multiple reps. It helps plan training percentages without requiring a risky max attempt.
Use it when you want to: Estimate a one-rep max without testing a true max. Compare Epley and Brzycki estimates.
What to enter
Good answers start with clean inputs. Before calculating, check the labels, units, and dates so the tool is solving the same problem you actually have.
- Enter the weight lifted and the number of completed reps.
- Use a set that was close to hard but performed with good form.
- Keep reps in a normal estimating range; very high reps are less reliable.
Example walkthrough
Try the calculator example: Bench example: 100 kg x 5. The example result is Estimated 1RM about 117 kg.
- For 100 kg x 5, the Epley formula adds one sixth of the weight to the original load.
- The result is an estimated 1RM of about 117 kg, with another formula shown for comparison.
Formula and steps
The main estimate uses Epley: one-rep max = weight x (1 + reps / 30). Brzycki is shown as a comparison.
The formula line on the calculator page is there so the answer is not a mystery. Read it when you need to understand where the number came from.
How to read the answer
Use the result as an educational estimate. For health, pregnancy, nutrition, kidney, alcohol, or training decisions with real consequences, get qualified professional guidance.
- Use the estimate to plan percentages, not to prove what you must lift today.
- If formulas disagree, treat the range as uncertainty.
Common mistakes to avoid
Most bad calculator results come from a small input mistake or from using a good estimate for the wrong decision.
- Do not test heavy singles without proper setup and supervision.
- Do not use failed reps or partial reps as clean input.
- Do not expect the same estimate across every lift.
What to try next
A related calculator can help check the same topic from another angle instead of relying on one number.
- Use Protein Calculator for nutrition planning around training.
- Use Target Heart Rate Calculator for conditioning work.
Sources and safety notes
This guide uses public-health, clinical, or peer-reviewed references where the calculator needs a specific formula or interpretation boundary.
Source links are provided for transparency, but they do not turn the calculator into medical advice or a replacement for professional care.
Examples from the calculator
Estimated 1RM about 117 kg
Estimated 1RM about 154 kg
Estimated 1RM about 76 kg
Common questions
What can I use the One Rep Max Calculator for?
Use it for quick educational estimates, planning, comparison, and trend checks. Health and fitness results should be interpreted with context, not as a diagnosis.
How does the One Rep Max Calculator calculate the result?
The main estimate uses Epley: one-rep max = weight x (1 + reps / 30). Brzycki is shown as a comparison.
Is this medical advice?
This is training math, not a safety guarantee. Do not attempt heavy max lifts without appropriate technique, equipment, and supervision.
Related tools
- Calories Burned Calculator Estimate exercise calories from MET, body weight, and duration.
- Target Heart Rate Calculator Estimate exercise heart-rate zones from age and intensity.
- Protein Calculator Estimate protein grams per day from body weight and target factor.
History, privacy, and copying
Recent answers stay visible in the page while you work. The history is kept only in the current browser tab and is not sent to a server.
Copy answer copies the expression and result so you can paste it into notes, homework, a message, or another document.