This one rep max calculator estimates a 1RM with the Epley formula from the weight you lifted and how many reps you completed. Enter weight and reps to get an estimated max.
Lifters use it to set training percentages without testing a true single every cycle. It is an estimate, so treat it as a guide beside bar speed and form quality.
How the estimate works
Estimated 1RM equals weight * (1 + reps / 30). More reps at the same weight raise the estimated max. The relationship is a simple model, not a perfect predictor for every lifter.
Worked example
Weight 100, reps 5. Estimated 1RM = 100 * (1 + 5/30) = about 116.67.
| Input | Value |
|---|---|
| Weight lifted | 100 |
| Reps | 5 |
| Estimated 1RM | ~116.67 |
How to use the fields
- Weight is the load on the bar or machine for the set.
- Reps are clean completed repetitions with your normal range of motion.
- Use the same unit system consistently when converting to percentages later.
Programming with the estimate
Once you have a 1RM estimate, multiply by 0.70, 0.80, or 0.85 for common working set targets. Recalculate when your best recent set changes by a meaningful amount. If bar speed slows sharply or form breaks, lower the working weight even if the math says otherwise.
Common mistakes
- Counting ugly reps that would not pass a meet standard
- Estimating from 20 plus reps where formulas drift
- Updating the max every easy session and inflating percentages
- Ignoring fatigue, sleep, and stress that change daily strength
Safety notes
Warm up, use collars, and arrange a spotter for heavy attempts. An estimate exists so you do not need to grind maximal singles on tired days. Stop a set if pain is sharp rather than normal effort discomfort.
When to refresh the estimate
Update after a clear PR on a clean set in the 3 to 6 rep range, or after a planned deload when performance returns. Avoid chasing daily fluctuations from poor sleep or stress. A stable estimate keeps percentage based programs coherent from week to week.
If you switch from barbell to a machine variation, compute a separate estimate for that movement. Carryover is imperfect, and using a barbell max on a different lever can overload joints.
Percentage examples
- At an estimated 1RM of 116.67, about 80 percent is roughly 93.
- About 70 percent is roughly 82 for higher rep hypertrophy work.
- Round to plates you own rather than chasing exact decimals.
- Cut load if bar speed collapses or form degrades mid set.
Those simple conversions keep the Epley estimate connected to the weights you actually load.
Warm up to the estimator set
Build to the working set with gradual warm ups so the recorded reps represent true strength, not a cold grind. Stop the estimator set one or two reps before form fails. Feeding failed reps into Epley overstates the max and pushes later percentages too high.
Beginners should favor conservative estimates and technique coaching over frequent max testing. Intermediate lifters can refresh estimates every training block. Advanced lifters may keep separate estimates for competition pause styles versus touch and go training styles.
Track the estimate beside body weight and sleep notes. Strength swings often have simple recovery explanations before they need a formula change.
Accessory lifts
Presses, rows, and single joint work can use the same Epley math, but the resulting max is for that lift only. Do not take a bench estimate and apply it unchanged to an incline variation with a different strength profile.
When in doubt, estimate again from a clean set on the exact variation you will train, then set percentages from that number.
Recalculate after any deliberate technique change such as a longer pause or a closer grip, because the effective max often shifts even when the labeled weight looks familiar.
Keep the unit system consistent across sessions so percentage charts remain comparable month to month.
Limitations
Different formulas (Brzycki, Lombardi, and others) can disagree by several percent. Machine leverage and pause styles also change carryover. Use Epley here as one consistent yardstick inside this tool, then listen to performance in the gym.
For related unit and percent checks while you plan materials, try the unit converter or the percentage calculator.