Estimate your one-rep max from any set between 2 and 30 reps using five scientifically validated formulas. See how each formula compares, plan percentage-based training loads, and generate warm-up pyramids — all without ever attempting a true maximal lift.
Pro tip: These formulas are most accurate between 2 and 10 reps. Above 10 reps, the estimates diverge significantly because fatigue becomes more of a factor than raw strength. For the most reliable estimate, use a weight you can lift for 3 to 5 reps with good form.
| Percentage | Reps | Weight |
|---|---|---|
| 100% | 1 | 0 lb |
| 95% | 2 | 0 lb |
| 90% | 4 | 0 lb |
| 85% | 6 | 0 lb |
| 80% | 8 | 0 lb |
| 75% | 10 | 0 lb |
| 70% | 12 | 0 lb |
| 65% | 15 | 0 lb |
A progressive warm-up plan based on your estimated 1RM. Gradually ramp up to your working weight while priming your nervous system.
| Set | % of 1RM | Weight | Reps |
|---|
How to Use the One-Rep Max Calculator
Enter the weight you lifted and the number of reps you completed. The calculator instantly estimates your one-rep max using five well-known strength formulas, then averages them for the most balanced prediction. Toggle between pounds and kilograms, and the results update in real time. Below the hero result you will find a formula comparison showing how each equation arrives at a slightly different number, plus a percentage chart that converts your 1RM into practical training loads for sets of 2 through 15 reps. Subscribers also get an exercise selector to label results and a warm-up pyramid that builds from 50 percent up to 90 percent of your max.
What Is a One-Rep Max and Why Does It Matter?
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with correct form. It serves as the foundation for percentage-based training, which is how most structured strength programs prescribe intensity. Knowing your 1RM lets you program sets at specific percentages — for example, 5×5 at 80 percent or 3×3 at 90 percent — so that every workout targets the right stimulus for strength, hypertrophy, or power. Without a reliable 1RM, programming is guesswork and progression stalls.
The Five 1RM Formulas Explained
Epley is one of the oldest and most widely cited formulas. It multiplies your weight by (1 + reps/30) and tends to produce slightly higher estimates at higher rep ranges. Brzycki uses a ratio of 36/(37 − reps) and is considered very accurate between 1 and 10 reps, though it becomes mathematically unstable above 36 reps. Lander applies a linear regression model — (100 × weight) / (101.3 − 2.67123 × reps) — and tracks closely with Brzycki for low rep counts. Lombardi raises reps to the 0.10 power, making it the most conservative formula at very high rep ranges. O’Conner is the simplest: weight × (1 + reps/40). By averaging all five, this calculator smooths out the individual biases of each formula and gives you a single, dependable estimate.
Why You Should Estimate, Not Test, Your 1RM
True one-rep max testing carries real injury risk, especially for intermediate lifters who lack the experience to grind through a maximal attempt with safe technique. A missed bench press can pin you under the bar; a failed squat can buckle your knees or compress your spine. Even with spotters, the nervous system stress of a true max takes days to recover from, disrupting your training week. Estimating your 1RM from a submaximal set of 3 to 5 reps gives you a number that is accurate enough for programming while keeping you healthy and in the gym consistently. Save true max attempts for competition day or scheduled peaking blocks where recovery is planned around the effort.
How to Use Percentage-Based Training
The percentage chart below your 1RM estimate is the bridge between knowing your max and applying it. A common hypertrophy block might prescribe 4 sets of 8 at 75 to 80 percent, while a peaking block might call for triples at 90 percent. The rep ranges shown — from 1 rep at 100 percent down to 15 reps at 65 percent — cover the full spectrum of strength, hypertrophy, and muscular endurance. Round the calculated weights to the nearest plate increment available in your gym (typically 5-pound or 2.5-kilogram jumps) and adjust by feel. If the prescribed weight moves slowly on the first rep, drop by one increment; if it flies up, you may be due for a 1RM retest.
Common Mistakes in Strength Training Programming
Training too heavy too often. Spending every session above 90 percent accumulates fatigue faster than you can recover, leading to plateaus and overuse injuries. Most of your volume should sit between 65 and 85 percent. Ignoring rep quality. A set of 5 that degrades into ugly grinding reps is not the same stimulus as 5 clean reps. Use a weight where you can maintain technique throughout the set — typically leaving one or two reps in reserve. Never retesting. Your 1RM changes as you get stronger. Recalculate every 8 to 12 weeks, or whenever a working weight starts feeling noticeably lighter. Skipping warm-ups. Jumping straight to working sets is the fastest path to a pulled muscle. A proper warm-up pyramid gradually loads the joints, activates the target muscles, and primes your nervous system for heavy work. Even five minutes of ramping sets can make your top sets feel smoother and reduce injury risk dramatically.
Looking for related tools? Try our Macro Calculator to fuel your strength training with the right nutrition, or explore all Health & Fitness tools.