HOW IT WORKS
Our 1RM methodology
Transparent estimates are better than mysterious strength scores.
Epley formula
Estimated 1RM = weight × (1 + reps ÷ 30). For a true single repetition, we return the entered weight exactly. This is the primary number displayed throughout the site.
Brzycki formula
Estimated 1RM = weight × 36 ÷ (37 − reps). We show this estimate alongside Epley to illustrate uncertainty. We restrict calculator inputs to 1–12 reps and recommend interpreting high-rep results cautiously.
What these numbers mean
These are estimates from a submaximal performance, not verified maximums. Use completed reps with consistent technique, ideally from a set performed close to failure. Longer sets, fatigue, unfamiliar equipment, and exercise selection can make predictions less dependable. Weight percentages are simple fractions of the Epley estimate.
Exercise limits
Standard formulas aren't meaningful for exercises measured by distance, assistance, skill, or repetitions of your bodyweight. Our exercise pages flag those cases rather than offering a misleading estimate. Different machines and dumbbell-versus-barbell loads should never be treated as interchangeable.
Strength ranking data
Numerical Beginner-to-Exceptional standards are intentionally withheld until we have reliable source data, a documented comparison population and permission to use the data. Exercise pages should never claim precise strength percentiles without that foundation.
Updated
October 18, 2026
Strength starts with a good baseline.
Calculate a reliable starting estimate and build your next workout from there.