Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Estimate your one-rep max from a weight and rep count using the Epley formula.
116.7
This tool estimates your one-rep max (1RM) -- the maximum weight you could lift for a single rep -- from a weight and rep count you've actually performed, using the Epley formula (1985), one of the two most widely used 1RM estimation formulas alongside Brzycki.
Enter the weight you lifted and the number of reps you completed with it. Your estimated 1RM appears instantly, along with common training percentages.
1RM = Weight × (1 + Reps / 30)
Most accurate for rep ranges under about 10; accuracy decreases at higher rep counts.
Use your estimated 1RM to plan training percentages (e.g. 80% for 5-rep sets) without actually testing a true 1-rep max, which carries higher injury risk, especially for less experienced lifters.
Suppose you complete 5 clean reps with 100 (in pounds or kilograms, whichever unit you use). The Epley calculation is 100 x (1 + 5 / 30) = 100 x 1.1667, which is about 116.7. The percentage tiles then show 80 percent at about 93.3, 70 percent at about 81.7, and 60 percent at 70.0. Because the tool does not convert units, the answers are in the same unit as the weight you entered. If you had done 10 reps at 100 instead, the estimate would be 100 x (1 + 10 / 30) = 133.3, which shows how strongly the rep count drives the result.
1RM = weight x (1 + reps / 30). Example: 100 x (1 + 5 / 30) = 116.7.
The three tiles give quick working weights: 80 percent for sets around five reps, 70 percent for around ten, and 60 percent for around fifteen. In the example above, that translates to roughly 93 for fives, 82 for tens, and 70 for fifteens. Treat these as starting points. Rounding to the plates you own is normal, and how many reps you actually get at a given percentage varies from person to person and lift to lift.
An estimate is not a guarantee that you can lift that weight once. It varies between exercises, and lifts that involve large muscle groups tend to behave differently from isolation moves. Sleep, nutrition, warm-up, and fatigue all change day-to-day performance. If you decide to test an actual max, use a spotter or safety pins, warm up progressively, and stop if form breaks down. Beginners, people returning from injury, and anyone with joint or heart concerns should ask a qualified coach or clinician before attempting near-maximal lifts. This page is educational and is not medical advice.
Reasonably accurate for rep ranges under 10, but formula-based estimates diverge more from a true 1RM at higher rep counts (15+) -- treat it as a solid planning estimate, not an exact number.
A true 1RM test carries higher injury risk, especially with improper form or insufficient warm-up -- an estimated 1RM from submaximal sets is generally safer for programming purposes.
It's a linear approximation that works well in the typical strength-training rep range, but the relationship between reps and % of max isn't perfectly linear across the full range, so accuracy degrades at very high rep counts.
Either. The tool does no unit conversion, so the result is in the same unit you entered.
The tool accepts 1 to 20 reps because the estimate becomes less reliable at higher counts.
You may have stopped short of failure, or your reps may have been slower or stricter than your best. Estimates depend heavily on how hard the set was.
The tool uses Epley for all of them. Individual lifts can deviate, so compare your estimate with real training results over time.
Reference: Centers for Disease Control and Prevention