One Rep Max (1RM) Calculator
Estimate your one rep max from any submaximal set using the Epley, Brzycki, or Lombardi formulas, with training percentages and rep-max projections.
One Rep Max (1RM) Calculator
Units
Your set
A hard set of 3 to 6 reps gives the closest estimate.
Formula
Training percentages
| % of 1RM | Weight | Typical use |
|---|
Rep max projections
| Reps | Weight |
|---|
Rep-max projections always use the Epley formula for stability across rep ranges.
Estimates only. A calculated 1RM is a planning tool, not a tested max. Warm up properly, use a spotter on heavy attempts, and stop a set the moment form breaks down.
How a 1RM calculator works
A one rep max calculator takes the weight you actually lifted and the reps you finished, then runs a regression formula to project what a single all-out rep would look like. The set has to be submaximal: a clean set taken close to failure, but not a true grind. Sets in the 3 to 6 rep range give the cleanest projection because the relationship between reps and 1RM is well documented at low rep counts.
Testing a true 1RM is rarely necessary for programming. A working set already tells you most of what you need to know, and skipping the max attempt saves your nervous system for the actual program. Three classic formulas (Epley, Brzycki, and Lombardi) have been around long enough that any modern strength program assumes you have a 1RM number to anchor percentages to.
Comparing Epley, Brzycki, and Lombardi
Each formula was published in a different year and validated against a slightly different rep range. Epley (1985) is a linear approximation: 1RM equals weight times (1 plus reps divided by 30). It is the workhorse of strength coaching and holds up well at 7 to 10 reps. Brzycki (1993) uses the formula weight times 36 divided by (37 minus reps), which is tight and accurate at 2 to 6 reps but compresses badly above 12 reps because the denominator shrinks toward zero.
Lombardi (1989) is the gentlest of the three: weight times reps raised to the 0.10 power. It curves more slowly than the others, which makes it the best fit for sets of 10 to 15 reps where the linear formulas overshoot. The Average option on this calculator splits the difference, so you get a reasonable number regardless of which rep range you trained in. For research-grade comparisons of the seven most common 1RM equations, LeSuer and colleagues (1997) remains the cleanest peer-reviewed reference.
Using 1RM percentages in real training programs
Percentage-based programs are the reason a 1RM number matters at all. Jim Wendler's 5/3/1 sets a Training Max equal to 90% of your 1RM, then runs working sets at 65, 75, 85, and 95% of that Training Max across the cycle. StrongLifts and the basic linear 5x5 templates sit between 70 and 85% of 1RM most weeks. Westside-style dynamic effort sessions use 50 to 60% with bands or chains to train bar speed instead of absolute load.
The training percentages table on this page is the same lookup chart that lives in the back of most strength programming books. Pick the percentage your program calls for, find the weight, and load the bar. Recalculate the 1RM whenever you hit a rep PR or finish a meso cycle, so the percentages keep matching the lifter you are today.
Tracking strength gains across a 75-day block
Recalculate at week 1, week 6, and week 11 of a 75-day challenge to see your strength curve next to body weight and workout streaks. Log the result inside Reset75 as a measurement task so the number lives next to the rest of your check-ins. Pair this with the macro calculator for protein targets, the calorie deficit calculator if you are cutting while preserving strength, and the two-a-day workout planner to structure heavy and accessory sessions. Lifters who want to wrap the whole strength block inside a structured challenge can run the 75 Tough tracker alongside it.
Frequently Asked Questions
Common questions about one rep max (1rm) calculator
How accurate is a 1RM calculator?
For sets of 2 to 6 reps, estimates usually land within 5% of a tested max. Accuracy drops above 10 reps because endurance starts to dominate over pure strength, so a hard set of 3 to 5 reps gives the cleanest projection.
Which 1RM formula is most accurate: Epley, Brzycki, or Lombardi?
Brzycki tends to edge ahead at 2 to 6 reps, Epley at 7 to 10 reps, and Lombardi holds up best at 10 to 15 reps. Averaging the three smooths out the differences for most lifters, which is why the calculator defaults to Average.
Should I actually test my 1RM?
Most lifters do not need to. A true 1RM test stresses the central nervous system and adds injury risk. An estimate from a working set gives you about 95% of the practical information without the recovery cost.
How often should I recalculate my 1RM?
Every 4 to 8 weeks, or whenever you hit a clean rep PR. Programs like 5/3/1 explicitly add 5 lb (upper body) or 10 lb (lower body) to your training max each cycle so the number stays current.
What is the difference between 1RM and Training Max?
Your true 1RM is the most you can lift once. Your Training Max (used in 5/3/1) sits at about 90% of that, so working sets stay achievable across a full cycle without burning you out by week three.
What is RPE and how does it relate to 1RM?
RPE (Rate of Perceived Exertion) on the 1 to 10 scale describes how hard a set felt. RPE 10 is a true 1RM-equivalent effort. RPE 8 is roughly 2 reps left in the tank, which maps to about 85 to 90% of 1RM at low reps.
Can beginners use 1RM percentages?
Yes, but recalculate often. Newer lifters add strength quickly, so a 1RM estimated this month will likely be too light in 4 weeks. Use the two-a-day workout planner to structure volume around the new numbers.
Why does my Brzycki estimate look low at high reps?
Brzycki uses a hard-coded constant (37) that compresses estimates as reps climb. Above 10 reps, switch to Epley or Lombardi for a more realistic projection, or just trust the Average option.