One Rep Max Calculator
PrintTraining Percentages (Intensity Zones)
| Percentage | Target Weight | Reps Target |
|---|---|---|
| 100% 1RM | 175.0 lbs | 1 rep |
| 95% | 166.3 lbs | 2 reps |
| 90% | 157.5 lbs | 3 reps |
| 85% | 148.8 lbs | 4-5 reps |
| 80% | 140.0 lbs | 6-7 reps |
| 75% | 131.3 lbs | 8-10 reps |
| 70% | 122.5 lbs | 11-12 reps |
| 65% | 113.8 lbs | 15 reps |
Formula Comparison Table
| Formula | Estimated 1RM |
|---|---|
| Epley Formula | 175.0 lbs |
| Brzycki Formula | 168.8 lbs |
| Lander Formula | 170.5 lbs |
| Lombardi Formula | 176.2 lbs |
| O'Conner Formula | 168.8 lbs |
| Wathan Formula | 171.3 lbs |
The One Rep Max Calculator (1RM Calculator) is an essential strength training tool designed to estimate the maximum weight you can lift for a single, full-range repetition without risking injury from true maximal testing. Utilizing validated exercise science equations—including the Brzycki, Epley, Lander, and Lombardi formulas—this tool converts submaximal multi-rep performance into precise 1RM benchmarks.
Whether programming strength cycles (5/3/1, linear periodization), calculating percentage warm-up loads, or tracking progress on bench press, back squats, and deadlifts, this calculator optimizes your workout intensity.
The 1RM Mathematical Formulas
Submaximal repetitions to fatigue are converted into estimated One Rep Max (1RM) using four industry-standard formulas:
1. Epley Formula
1RM = Weight * (1 + Reps / 30)
Widely preferred for rep ranges between 2 and 10 reps.
2. Brzycki Formula
1RM = Weight * (36 / (37 - Reps))
Highly accurate for lower rep ranges (1 to 8 reps).
3. Lander Formula
1RM = (100 * Weight) / (101.3 - 2.67123 * Reps)
4. Lombardi Formula
1RM = Weight * Reps^0.10
Percentage of 1RM & Repetition Benchmark Table
The table below provides training load percentages, target repetition capabilities, and working weight breakdowns for an athlete with an estimated 300 lb One Rep Max (1RM):
| % of 1RM | Max Reps Possible | Working Weight (300 lb 1RM) | Training Zone Purpose | RPE Rating Equivalent |
|---|---|---|---|---|
| 100% | 1 Rep | 300 lbs | Maximal Neuromuscular Test | RPE 10 (Maximum Effort) |
| 95% | 2 Reps | 285 lbs | Peak Strength / Heavy Doubles | RPE 9.5 |
| 90% | 3 – 4 Reps | 270 lbs | Heavy Strength Building | RPE 9.0 |
| 85% | 5 – 6 Reps | 255 lbs | Hypertrophy & Strength Hybrid | RPE 8.5 |
| 80% | 7 – 8 Reps | 240 lbs | Muscle Hypertrophy Zone | RPE 8.0 |
| 70% | 11 – 12 Reps | 210 lbs | Muscular Endurance & Volume | RPE 7.0 |
Step-by-Step 1RM Calculation Worked Example
A lifter performs a set of Bench Press lifting 225 lbs for 5 clean repetitions to failure.
Step 1: Calculate Using Epley Formula
1RM_Epley = 225 * (1 + 5 / 30) = 225 * 1.1667 = 262.5 lbs
Step 2: Calculate Using Brzycki Formula
1RM_Brzycki = 225 * (36 / (37 - 5)) = 225 * (36 / 32) = 225 * 1.125 = 253.1 lbs
Step 3: Average the Results
Estimated 1RM Average = (262.5 + 253.1) / 2 = 257.8 lbs (≈ 258 lbs)
Step 4: Calculate 80% Hypertrophy Working Weight
80% Working Weight = 258 lbs * 0.80 = 206.4 lbs (Round to 205 lbs)
Worked Example Summary: Lifting 225 lbs for 5 reps indicates an estimated One Rep Max of 258 lbs, yielding an 80% hypertrophy working weight of 205 lbs for 8-rep sets.
Frequently Asked Questions
Why are submaximal 1RM calculations safer than true 1RM testing?
Testing a true 1RM places extreme neurological and mechanical stress on tendons, ligaments, and joints, significantly raising the risk of acute injury (such as muscle tears). Estimating 1RM from 3-to-6-rep sets yields high accuracy while maintaining safe form.
Why do 1RM formulas become less accurate above 10 repetitions?
As repetitions increase above 10, performance is limited more by cardiovascular endurance, lactic acid buffering, and local muscular fatigue rather than maximal neural force production, causing 1RM formulas to overestimate actual maximal strength.
What is RPE in strength training?
RPE (Rating of Perceived Exertion) measures set difficulty on a 1-to-10 scale based on RIR (Reps in Reserve). RPE 10 means 0 reps left in the tank (true failure); RPE 9 means 1 rep left; RPE 8 means 2 reps left.
Should I use the same 1RM formula for Bench Press and Deadlifts?
The Brzycki formula is generally preferred for upper-body compound movements (Bench Press, Overhead Press) performed between 1 and 8 reps. The Epley formula is preferred for lower-body compound lifts (Squats, Deadlifts) performed up to 10 reps.