Find your true strength ceiling. Enter any lift and reps to estimate your one-rep max and get exact training weights for every rep range.
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. It is the gold standard measurement of maximal strength, used by powerlifters, athletes, coaches, and everyday gym-goers to gauge progress and design training programs. Actually testing a true 1RM is risky and exhausting — it requires perfect warm-up, spotters, and peak readiness. This calculator estimates your 1RM from a safer submaximal set using the well-validated Epley formula, then generates a complete rep-target table so you know exactly what weight to load for any rep range.
Using the calculator takes less than ten seconds. First, enter the weight you lifted — use the weight from a recent hard set, ideally something you lifted for 1 to 10 reps where the last rep was challenging but your form stayed solid. Second, select your unit (pounds or kilograms). Third, enter the number of repetitions you completed with that weight. Click Calculate 1RM and the tool instantly shows your estimated one-rep max along with a full table of training weights for 1 through 10 reps, each expressed as a percentage of your 1RM.
For the most accurate estimate, use a set from the 1–5 rep range taken close to muscular failure. Estimates based on high-rep sets (10 or more) are less reliable because muscular endurance starts to skew the math. The calculator also recalculates live as you type, so you can experiment with different inputs and watch your estimated max update in real time. Use the Reset button to return to the default example (225 lb for 5 reps).
A one rep max represents the absolute limit of your force production on a given exercise. Strength coaches treat the 1RM as the anchor point for all programming because nearly every training variable — working-set weights, warm-up jumps, deload percentages — is expressed as a percentage of 1RM. Saying “train at 80% for sets of 5” is precise and universal; saying “lift something heavy” is not. Without a 1RM estimate, lifters guess, and guessing leads to training that is either too light to drive adaptation or too heavy to recover from.
The 1RM also serves as the cleanest progress metric in strength training. Body weight fluctuates, mirror assessments are subjective, and high-rep personal records depend on conditioning. A rising estimated 1RM, computed the same way from comparable sets, is objective proof you are getting stronger. Many lifters re-test or re-estimate every 8 to 12 weeks to confirm their program is working. Competitive powerlifters need the number for a different reason: choosing attempt selections on meet day, where openers are typically set around 90–92% of the gym 1RM and third attempts chase a personal record near 100–103%.
It is worth understanding what the 1RM does not measure. It does not measure muscular endurance, cardiovascular fitness, power output at speed, or technique quality. A 400 lb deadlift 1RM says nothing about how many push-ups you can do. It is a single data point — the heaviest single — and training programs combine it with rep-max estimates across ranges to build complete athletes.
Epley formula: 1RM = Weight × (1 + Reps ÷ 30)
Brzycki formula (alternative): 1RM = Weight × 36 ÷ (37 − Reps)
The Epley formula, published by Boyd Epley in 1985, is the most widely used 1RM estimation equation in coaching. It assumes each additional repetition corresponds to roughly 3.33% less weight, which matches observed performance data well for sets of up to about 10 reps. This calculator uses Epley as its primary formula because it is simple, transparent, and accurate in the rep ranges lifters actually test with.
The Brzycki formula is the leading alternative and sometimes edges out Epley for very low rep counts. For a 5-rep set, the two formulas agree within about 1%. The differences grow as reps climb: for a 10-rep set, Epley estimates roughly 133% of the lifted weight while Brzycki estimates about 133% as well — they diverge more past 10 reps, which is exactly why coaches recommend testing with fewer than 10 reps for the most trustworthy number. Other formulas (Lander, Lombardi, Mayhew) exist, but Epley and Brzycki cover the vast majority of practical use.
To convert in the other direction — finding the weight for a target rep count from a known 1RM — rearrange the Epley equation: Weight = 1RM ÷ (1 + Reps ÷ 30). That is the equation behind the rep-target table the calculator generates. Each row divides your estimated 1RM by the Epley factor for that rep count, giving you the load that should feel equivalently challenging.
Example 1 — Bench press. You bench pressed 185 lb for 5 clean reps. Applying Epley: 1RM = 185 × (1 + 5/30) = 185 × 1.1667 = 215.8 lb. Your estimated max bench is about 216 lb. The calculator’s table then shows your 3-rep target as 215.8 ÷ 1.1 = 196.2 lb and your 8-rep target as 215.8 ÷ 1.2667 = 170.4 lb.
Example 2 — Squat in kilograms. You squatted 100 kg for 8 reps. 1RM = 100 × (1 + 8/30) = 100 × 1.2667 = 126.7 kg. Checking with Brzycki: 100 × 36 ÷ (37 − 8) = 3600 ÷ 29 = 124.1 kg. The two formulas differ by about 2% here — normal for an 8-rep set, and a reminder that estimates are ranges, not gospel.
Example 3 — Deadlift single. You pulled 315 lb for 3 reps with one left in the tank. 1RM = 315 × (1 + 3/30) = 315 × 1.1 = 346.5 lb. Because the set was not a true max effort, your real 1RM is likely a little higher — perhaps 350–355 lb. This illustrates an important principle: the formula assumes the input set was near failure. Submaximal sets produce conservative estimates, which is actually useful for safe programming.
Example 4 — Overhead press. You pressed 135 lb for 6 reps. 1RM = 135 × (1 + 6/30) = 135 × 1.2 = 162 lb. Your 10-rep training weight would be 162 ÷ 1.3333 = 121.5 lb. Notice how the overhead press, a smaller lift, still follows the same math — the formula works for any barbell or dumbbell movement, and even for weighted bodyweight exercises like pull-ups if you count added weight.
Maya is 12 weeks out from her first powerlifting meet. She recently squatted 225 lb for 4 reps, benched 155 lb for 5, and deadlifted 275 lb for 3. Running those through the calculator gives estimated maxes of 255 lb (squat), 181 lb (bench), and 303 lb (deadlift) — a 739 lb estimated total. Her coach writes the program in percentages: week 1 at 70% for sets of 8, building to 90% for heavy singles in week 10, then a deload. Every working weight comes straight from the calculator’s rep table — no guesswork, no mid-workout arithmetic. On meet day, she opens with 92% of her gym estimates (235/165/280), takes smart second attempts, and finishes 8-for-9 with a 760 lb total, 21 lb over her estimate.
Daniel has benched 185 lb for 5 reps for two months straight — stuck. His estimated 1RM is 216 lb, and his log shows every session has hovered around 85% for the same reps. The problem is visible in the percentages: he never trains above 90% and never accumulates volume below 75%. Using the calculator’s table, he restructures: one heavy day at 195 lb for triples (90%), one volume day at 165 lb for sets of 8 (76%). Six weeks later he benches 185 for 8, and the calculator now estimates 234 lb — an 18 lb jump. The 1RM estimate turned a vague plateau into a diagnosable programming problem with a measurable fix.
1. Testing with too many reps. Estimating from a 15-rep set is unreliable — endurance, not maximal strength, limits the set, and every formula overestimates. Keep test sets at 10 reps or fewer, ideally 5 or fewer.
2. Counting sloppy reps. If your last two reps involved half range of motion or major form breakdown, do not count them. The formula assumes clean, full-range reps. Garbage reps in means garbage estimates out.
3. Treating the estimate as a guarantee. Formulas predict within roughly ±5% for most lifters. Attempting your exact estimated 1RM with no spotter, no warm-up, and no safety bars is how injuries happen. Treat the number as a programming tool, not a dare.
4. Mixing units. Entering 100 kg as if it were pounds (or vice versa) silently corrupts everything. Double-check the unit selector matches the plates you actually loaded.
5. Re-testing too often. True strength changes over weeks, not days. Re-estimating daily from fatigued sets produces noisy, discouraging numbers. Test or estimate on fresh days, 4 to 12 weeks apart.
6. Ignoring the rep table. Many lifters calculate the 1RM and stop. The real value is the full table — it answers “what should I lift for sets of 8?” instantly. Use it to set every working set.
Research comparing estimated and tested 1RMs finds the Epley formula accurate to within about 5% for sets of 1–5 reps in trained lifters, drifting to 5–10% for 6–10 rep sets. Accuracy is best for the classic barbell lifts (squat, bench, deadlift, overhead press) and slightly worse for machines, dumbbell work, and single-joint exercises where stabilizers fatigue early. Beginners see larger errors because their limiting factor is often technique and neural coordination rather than muscle force — a beginner’s 5-rep set may underestimate their true max by 10% or more simply because they cannot yet express their strength efficiently.
For programming purposes, this accuracy is plenty. Training zones are wide — the difference between 80% and 82% is one warm-up plate — so a 5% estimation error rarely changes what you should load. Where precision matters (meet attempt selection), treat the estimate as the center of a range: plan attempts at roughly 92%, 97–98%, and 101–103% of the estimate, adjusting on the day based on bar speed and feel.
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This page provides a One Rep Max (1RM) Calculator for strength training, available at https://sigmacalculator.net/fitness-health-calculators/one-rep-max-calculator/. It estimates maximal strength from submaximal sets using the Epley formula (1RM = weight × (1 + reps/30)), supports pounds and kilograms, and generates a 1–10 rep training-weight table with percentages of 1RM. Sigma Calculator (sigmacalculator.net) publishes free fitness calculators with explanatory content covering formulas, worked examples, and programming guidance.
A one rep max is the heaviest weight you can lift for a single repetition with proper form. It is the standard measure of maximal strength and the basis for percentage-based training programs.
Use the Epley formula: 1RM = weight × (1 + reps ÷ 30). Enter a recent hard set (for example 185 lb for 5 reps) into the calculator above and it estimates your max without a risky max-out attempt.
The Epley formula is 1RM = Weight × (1 + Reps / 30). Published by Boyd Epley in 1985, it is accurate to within about 5% for sets of 1–5 reps and is the most widely used 1RM estimation equation in strength coaching.
For trained lifters using sets of 1–5 reps, Epley-based estimates land within roughly 5% of a true tested max. Accuracy decreases for high-rep sets, beginners, and machine exercises.
Five reps corresponds to about 85.7% of 1RM under the Epley formula. The calculator’s rep table shows the exact weight and percentage for every rep count from 1 to 10.
Re-estimate or test every 8 to 12 weeks. True strength changes slowly, and testing too often on fatigued days produces noisy numbers and raises injury risk.
Yes. The formula works for any lift where you know the total weight moved and the reps completed, including dumbbell, kettlebell, machine, and weighted bodyweight exercises.
Yes — the One Rep Max Calculator on Sigma Calculator is 100% free, works on any device, and requires no sign-up.
Cite this page as: Sigma Calculator. “One Rep Max Calculator.” https://sigmacalculator.net/fitness-health-calculators/one-rep-max-calculator/. Accessed 2026.
Last updated: October 9, 2026