Quick start
- Open the One Rep Max Calculator.
- Enter the weight lifted in kilograms 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
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- 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 clean reps. It helps compare Epley and Brzycki 1RM estimates and 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 in kilograms and the number of completed reps.
- Use a set that was hard but performed with full range of motion and consistent form.
- Keep reps at 30 or fewer; very high-rep sets are more about endurance and fatigue than max strength.
Example walkthrough
Try the calculator example: Bench example: 100 kg x 5. The example result is Epley about 116.67 kg; Brzycki about 112.5 kg.
- For 100 kg x 5, Epley is 100 x (1 + 5 / 30), which is about 116.67 kg.
- Brzycki gives a second estimate: 100 x 36 / (37 - 5), which is about 112.5 kg.
- The 80% training reference from the Epley estimate is about 93.33 kg.
Formula and steps
In plain language: Epley estimate = weight x (1 + reps / 30). Brzycki estimate = weight x 36 / (37 - reps), with the lifted weight used directly for a single rep. The page also shows 80% of the Epley estimate as training-load context. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
Read the formula note when you need to understand where the number came from, especially before comparing results over time.
How to read the answer
One-rep max estimates are training math, not proof that a heavy single is safe today. Use qualified coaching, safe equipment, and a spotter or safety setup when needed.
- Use the estimate to plan percentages, not to prove what you must lift today.
- If Epley and Brzycki disagree, treat the gap as uncertainty instead of pretending one number is exact.
Common mistakes to avoid
Most bad results come from a small input mistake or from using a rough estimate for a decision it cannot safely answer.
- Do not test heavy singles without proper setup and supervision.
- Do not use failed reps, forced reps, or partial reps as clean input.
- Do not expect the same estimate across every lift, rep range, fatigue level, or training block.
What to try next
A related health tool can help check the same topic from another angle, but one number should not replace proper care.
- 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.
Worked examples for One Rep Max Calculator
Epley about 116.67 kg; Brzycki about 112.5 kg
Epley about 154 kg; Brzycki about 148.24 kg
Epley about 76 kg; Brzycki about 74.48 kg
Epley about 192 kg; Brzycki about 185.14 kg
FAQ in plain language
When should I use the One Rep Max Calculator?
Use it for simple educational checks, trend tracking, or planning tasks like these: Estimate a one-rep max without testing a true max. Compare Epley and Brzycki estimates. It can help you understand a number, but it cannot explain your whole health situation.
What do the main One Rep Max Calculator inputs mean?
Enter the weight you lifted in kilograms and the number of clean reps you completed. Use a set with full range of motion and consistent form. Do not use failed reps, forced reps, partial reps, or a set above 30 reps as a clean input.
What is the One Rep Max Calculator doing with my inputs?
In plain language: Epley estimate = weight x (1 + reps / 30). Brzycki estimate = weight x 36 / (37 - reps), with the lifted weight used directly for a single rep. The page also shows 80% of the Epley estimate as training-load context. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
How should I read the One Rep Max Calculator result?
Read the Epley estimate as the main training estimate and the Brzycki line as a comparison. If the formulas disagree, treat the gap as uncertainty. Use the number for planning percentages, not as proof that a heavy single is safe today.
Which one-rep max formula should I trust?
Use Epley as the main estimate on this page and Brzycki as a comparison. If they are close, the estimate is more stable. If they are far apart, treat the range as uncertainty instead of chasing one exact number.
Why does the calculator limit reps to 30 or fewer?
Very high-rep sets measure endurance, pacing, and fatigue as much as max strength. The calculator stops at 30 reps so the answer stays in a practical strength-estimate range.
Should I use a failed rep or assisted rep?
No. Use only reps you completed with your own effort and clean form. Failed reps, forced reps, bouncing, shortened range of motion, or uneven technique can inflate the estimate.
Related tools
- Calories Burned CalculatorEstimate total and active exercise calories from MET, weight, and time.
- Target Heart Rate CalculatorEstimate target heart-rate zones by age or turn a timed pulse count into BPM.
- Protein CalculatorEstimate protein grams per day from body weight and target factor.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Health & FitnessBrowse the full category for related tools that help with the same job.
- All free toolsSearch the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guidesFind more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resourcesStart here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.