One-Rep Max (1RM) Calculator
Lift what's in front of you today — the estimate just tells you where the ceiling is.
Estimate your one-rep max from any weight and rep count using the Epley, Brzycki, Lombardi and Lander formulas. Your 1RM is the most you could lift once, and you can work it out from a normal hard set without ever attempting a risky true max. The calculator also prints a percentage-of-1RM training-load table and a relative-strength figure.
Estimates from a submaximal set using standard strength formulas — a planning guide only. Warm up, use a spotter for heavy lifts, and train within your ability.
How the estimate is worked out
What a 1RM is
Your one-rep max (1RM) is the heaviest weight you could lift for a single clean repetition of an exercise. Rather than actually attempting that top single — which is risky and needs a full warm-up and a spotter — you can estimate it from a submaximal set: a normal hard set of a few reps with a weight you can handle. The more reps you can do with a given weight, the higher your true max must be, and the formulas turn that relationship into a number.
The two main formulas
The default here is Epley: 1RM = weight × (1 + reps ÷ 30). The other classic is Brzycki: 1RM = weight × 36 ÷ (37 − reps). Both are most accurate at 1–6 reps and become rough above about 10 reps, where endurance rather than pure strength limits the set. Lombardi and Lander are further variants you can switch to; at low reps all four agree within a couple of kilograms.
Worked example
Say you lift 100 kg for 5 reps. Epley gives 100 × (1 + 5 ÷ 30) = 100 × 1.167 ≈ 117 kg. Brzycki gives 100 × 36 ÷ (37 − 5) = 100 × 36 ÷ 32 ≈ 112.5 kg. So your estimated one-rep max is roughly 112–117 kg depending on the formula — close enough to program your training around without ever testing a true single.
This is an estimate, not a guarantee. Your real max on the day depends on fatigue, technique, warm-up, sleep and the exact exercise. Treat the number as a training anchor, keep test sets to low reps, and always warm up and use safety equipment for heavy lifts.
Turning your 1RM into working weights
Once you have a 1RM, most training programs prescribe a percentage of it. The calculator prints a %1RM table so you can read the working weight for each training zone straight off your estimate:
- Maximal strength — ~85–95% of 1RM, low reps (about 2–5). This builds the ability to move heavy weight and is where powerlifters spend much of their time.
- Hypertrophy (muscle size) — ~67–80% of 1RM, moderate reps (about 6–12). The classic muscle-building range, with enough load and volume to drive growth.
- Power & speed — ~50–65% of 1RM, moved as fast as possible for low reps. Lighter bars moved explosively train rate of force, not just size.
So on a 117 kg estimated max, a hypertrophy day at 75% is about 88 kg, and a speed day at 60% is about 70 kg. Turn on rounding to snap those figures to the nearest 2.5 kg or 5 kg plate you actually load on the bar.
Relative strength
Add your bodyweight and the calculator shows relative strength = 1RM ÷ bodyweight. This is how lifters compare across sizes: a 117 kg lift at 80 kg bodyweight is about 1.46× bodyweight. It normalises for size, so a lighter lifter with a strong relative number can out-rank a heavier one on absolute load.
Which formula to use, and testing a true max
Epley, Brzycki, Lombardi and Lander
Each formula was fitted to a different group of lifters, so they read slightly differently. Epley (1 + reps ÷ 30) tends to read a little higher; Brzycki (36 ÷ (37 − reps)) a little lower. Lombardi uses a power curve (weight × reps0.10) and Lander a linear fit. At low reps they land within a couple of kilograms of one another; the gaps widen as reps climb. The practical rule is to pick one formula and stay with it so your numbers are consistent over time.
Keep test sets low
Estimates are most reliable from a genuinely hard set of 1–6 reps. Above about 10 reps, breathing, grip and endurance limit the set before true strength does, so the maths over-predicts your max. If light weights are all you have, take the lowest-rep hard set you can and treat the result as a ballpark.
Estimating beats maxing out
For most people, estimating avoids a risky true-max attempt where technique can fail under load. If you do choose to test a real max, do it only when experienced and warm: build up in progressively heavier singles, use a spotter or safety pins, and stop the moment form breaks down. The estimate is accurate enough to run a training block without ever attempting a true single.
❓ Frequently asked Frequently asked questions
How do you calculate one-rep max?
You estimate it from a submaximal set rather than actually lifting a true max. The most common method is the Epley formula: 1RM = weight × (1 + reps ÷ 30). Brzycki is the other popular option: 1RM = weight × 36 ÷ (37 − reps). For example, 100 kg for 5 reps gives about 117 kg by Epley and 112.5 kg by Brzycki. Both are most accurate for hard sets of about 1 to 6 reps and get rougher as the reps climb, because fatigue and technique start to dominate.
Which 1RM formula is most accurate?
No single formula wins for everyone — they were fitted to different groups of lifters and agree closely at low reps but diverge as reps rise. Epley tends to read a little higher and Brzycki a little lower at the same weight and reps, with Lombardi and Lander offering further variants. The practical answer is to pick one formula and use it consistently, and to keep your test set to about 5 reps or fewer, where all four formulas land within a couple of kilograms of each other.
How many reps should I use to estimate my 1RM?
Use a genuinely hard set of about 1 to 6 reps for the most reliable estimate. In that range the formulas are well validated and closely aligned. Above 10 reps the estimate becomes unreliable — endurance, breathing and grip start to limit the set before true strength does, so the maths over-predicts your max. If you can only train with lighter weights, take the lowest-rep hard set you can manage and treat the result as a ballpark.
What percentage of 1RM should I train at?
It depends on the goal. Maximal strength work usually sits at about 85 to 95% of 1RM for low reps, hypertrophy (muscle size) at roughly 67 to 80% for moderate reps, and speed or power work at about 50 to 65% moved fast. This calculator prints a percentage-of-1RM table from your estimate so you can read off the working weight for each zone, then round it to the nearest plate you actually have on the bar.
Is it safe to test my true one-rep max?
Estimating your 1RM from a submaximal set is the safer choice for most people, because it avoids a risky maximal attempt where technique can break down under load. If you do want to test a true max, do it only when you are experienced and well warmed up, build up in progressively heavier singles, use a spotter or safety pins, and stop if form fails. For most lifters the estimate is accurate enough to program training without ever attempting a true max.
Where these figures come from
The method here is standard strength-and-conditioning practice, not a country-specific rule. The estimation formulas and training-load ranges are the mainstream figures taught in exercise-science texts and used by coaches worldwide.
- Epley formula — 1RM = weight × (1 + reps ÷ 30), the most widely used estimation equation.
- Brzycki formula — 1RM = weight × 36 ÷ (37 − reps); Lombardi = weight × reps0.10; Lander as a linear alternative.
- Training-load zones — maximal strength ~85–95% of 1RM, hypertrophy ~67–80%, power/speed ~50–65%, in line with standard periodisation guidance.
- Relative strength — 1RM ÷ bodyweight, the usual way to compare lifters of different sizes.
Last checked: July 2026. This is a training estimate, not medical advice. Your true max varies with fatigue, technique, warm-up and the exercise — warm up properly, use a spotter or safety pins for heavy lifts, and check with your GP before maximal training if you have any health condition.
Select the question that matches where you are right now.
The headline number is your estimated one-rep max — the most you could lift once — worked out from the weight and reps you entered. The breakdown shows the figure from each formula and a percentage-of-1RM table of working weights for your training.
Use it as a training anchor. Set your working weights as a percentage of the estimate — heavier for strength, lighter and faster for power — and re-test with a fresh hard set every few weeks to track progress.
It is not a guaranteed lift on the day and not medical advice. Fatigue, sleep, warm-up and the specific exercise all move your real max. Treat it as a planning number, not a target to chase recklessly.
Estimating from a normal set avoids a risky true-max attempt where technique can fail under load. For most lifters the estimate is close enough to program around without ever pulling a true single.
Three things move the estimate the most: the weight and reps of your test set, the formula you pick, and how fresh you were when you lifted.
More reps at a given weight implies a higher max. But accuracy falls away above about 6 reps, so a heavy set of a few reps beats a light set of many for a trustworthy number.
Epley reads a touch higher, Brzycki a touch lower, with Lombardi and Lander as variants. At low reps they agree within a couple of kilograms — just stay on one formula for consistency.
A tired or sloppy set understates your strength; a well-warmed, clean set reflects it. Estimate from a set where the reps were hard but the form held, not a grinding failure set.
A few habits keep the estimate honest and your training safe.
Use a hard set of 1–6 reps to estimate. The formulas are best validated there, and all four agree closely, so the number you get is dependable.
Even estimated maxes lead to heavy training weights. Build up in warm-up sets, and use a spotter or safety pins whenever the bar is genuinely heavy.
Turn on plate rounding so your working weights snap to what you can actually load. Chasing an exact 88.3 kg wastes time — 90 kg on the bar is close enough.
Strength sits alongside the rest of your health picture. Pair your 1RM with body-composition and energy tools to round out your training.