Formula used here
The tool uses an Epley-style estimate: weight × (1 + reps ÷ 30), with the rep input capped at 12 for the calculation. The estimate becomes less reliable as fatigue, technique, exercise choice, and rep range change.
One Rep Max Calculator
Estimate one-rep max and training percentages from a recent set, then use ZenFit AI to organize strength workouts safely.
Estimate your targets
Enter the basics that shape this estimate, then adjust the numbers after the calculator loads.
exercise
weight used
reps completed
training goal
An estimated 1RM is a training reference
The result predicts a one-rep maximum from a recent submaximal set and provides 75% and 85% reference loads. It is not a requirement to attempt a maximal lift.
Apply the estimate conservatively
Use the percentage loads as a starting reference, then choose a load that matches stable technique and the session goal. A spotter or qualified coach matters more than a calculator when lifting heavy.
Method used
Uses the Epley-style one-rep max estimate. It is most useful for moderate rep ranges and should not encourage unsafe max attempts.
The estimate should be compared with real-world outcomes over time. Body weight trends, training performance, hunger, schedule, sleep, injury status, and consistency can all change what works in practice.
Important safety note
This tool is for general fitness education and planning context. It is not medical advice. If you are pregnant, managing a medical condition, recovering from an injury, changing medication, or unsure whether a calorie or training change is appropriate, speak with a qualified clinician.
Next step
Build the plan behind this result
Use the quiz to connect this tool's estimate to workouts, meals, progress tracking, and AI coach context around your real week.
Frequently asked questions
Should I test a true one-rep max?
Not always. Many lifters can plan effectively from submaximal sets, especially without a spotter or coach.
Is the one-rep max estimate exact?
No. It varies by exercise, rep range, technique, fatigue, and individual strength endurance.
Useful next estimates
Related tools
Workout Split Generator
Generate a practical weekly workout split based on training days, goal, equipment, and experience level.
Workout Routine Analyzer
See weekly sets, muscle coverage, and movement balance from the routine you already do. Free training audit, no signup or score.
Dumbbell Workout Generator
Generate a dumbbell workout preview for home, gym, or limited-equipment training, then personalize the full plan with ZenFit AI.
Lean Bulk Calculator
Estimate a lean bulk calorie surplus, protein target, and expected weekly gain range before personalizing your muscle gain plan in ZenFit AI.