Your one rep max, estimated from any hard set — six published formulas averaged, plus the percentage table for programming every training zone.
Your set
kg
5 reps
Estimated one rep max
114.9kg
Average of six formulas · they span 5 kg for this set
90% — heavy triples
103.4kg
80% — strength sets
91.9kg
70% — volume work
80.4kg
What each formula saysThe formulas agree closely at low reps and drift apart as reps climb — past ~10 reps the spread becomes the honest error bar.
Programming table — %1RM for your lifts
%1RM
Weight
Typical reps
Focus
100%
114.9 kg
1
Max strength
95%
109.2 kg
2
Max strength
90%
103.4 kg
3–4
Max strength
85%
97.7 kg
5–6
Strength
80%
91.9 kg
7–8
Strength / hypertrophy
75%
86.2 kg
9–10
Hypertrophy
70%
80.4 kg
11–12
Hypertrophy
65%
74.7 kg
13–15
Hypertrophy / endurance
60%
68.9 kg
16–20
Endurance
55%
63.2 kg
20+
Endurance
50%
57.5 kg
25+
Endurance
Formula estimates are most reliable from sets of 2–6 reps taken close to failure. Above ~10 reps all of them extrapolate, and the true error can exceed 10% — treat high-rep estimates as a rough ceiling, not a load to attempt.
Your rep-max curve
The weight you should be able to lift for every rep count, anchored to your estimated 1RM of 114.9 kg. Where the three lines separate is where the estimate stops being trustworthy.
EpleyBrzyckiWathan
What a 1RM is actually for
Your one rep max (1RM) is the heaviest weight you can lift once with acceptable form. Its real value is not bragging rights — it is the unit of programming. Nearly every serious strength program prescribes loads as percentages of 1RM (“5×5 at 80%”), because a percentage self-scales: the same program works for someone squatting 60 kg and someone squatting 220 kg. The catch is that actually testing a 1RM is fatiguing, technical and slightly risky, so lifters estimate it from submaximal sets instead. That estimate — often written e1RM — is what this calculator produces.
The formulas
All six published equations map the same input — weight lifted for a number of reps — onto a predicted single. For weight w and reps r:
At 2–6 reps they agree within a couple of percent — the calculator shows the spread as a bar chart so you can see it directly. Beyond that they diverge: Brzycki’s linear form gets conservative, Epley and O’Conner keep climbing, and Wathan’s exponential sits between them. Averaging the six is a simple, defensible way to avoid betting on one curve, and it is what the headline number does.
Why accuracy falls above ~10 reps
The formulas were fitted mostly on sets of one to ten reps. Above that, the rep–load relationship stops being a property of the formula and becomes a property of you: muscle fibre mix, training history and exercise choice change how many reps a given percentage allows. Two lifters with identical 1RMs can differ by five or more reps at 70%. A 15-rep set can still give a useful trend over time — just do not load the bar to the number it predicts.
Programming zones
Once you have an e1RM, percentages turn it into training decisions. The classic zones:
Zone
%1RM
Reps
Primary adaptation
Max strength
85–100%
1–6
Neural drive, skill with heavy loads
Hypertrophy
65–85%
6–15
Muscle size — the volume sweet spot
Endurance
<65%
15+
Muscular endurance, work capacity
The boundaries are soft — muscle grows across a wide rep range when sets are taken close to failure — but the zones remain a useful default. The full percentage table above translates each zone into actual plates for your current e1RM. Recalculate every few weeks: as your working sets improve, every percentage moves with them, which is the point of programming by percentage in the first place.
Testing a true 1RM safely
Estimates are enough for programming, but if you want the real number — for a meet, or just to know — test it deliberately:
Pick a low-fatigue day. Fresh, fed, well-slept, at the start of the session after a thorough warm-up.
Ramp in big-to-small jumps: roughly 5 reps at 50%, 3 at 70%, 1 at 80%, 1 at 90%, then singles adding 2–5% per attempt with 3–5 minutes of rest between.
Stop at the first grind. A rep that slows to a crawl but completes is your max; do not attempt another after it.
Use safety equipment — rack pins or a competent spotter for squat and bench. A missed deadlift can be dropped; a missed bench press cannot.
Expect the tested number to land close to your e1RM if your recent sets were honest — within about 5% is typical for the 2–6 rep range.
Strength is built in the kitchen too
Progressive overload only works with the raw material to recover: aim for roughly 1.6–2.2 g of protein per kilogram of body weight — the protein calculator gives your exact number — and enough total energy that hard sets do not run at a chronic deficit. If you are unsure where maintenance sits, the TDEE calculator is the place to start.
Frequently asked questions
How do I calculate my 1RM without maxing out?+
Take a recent hard set — weight and reps — and run it through an estimation formula. Lifting 100 kg for 5 reps estimates roughly a 112–117 kg one rep max depending on the formula. This calculator averages six published formulas, which is more robust than trusting any single one.
Which 1RM formula is most accurate?+
For sets of 2–6 reps they all land within a few percent of each other, so the choice barely matters. Brzycki tends to read conservative at higher reps, Epley and Wathan more generous. Averaging several formulas, as this calculator does, smooths out the individual biases.
Is a 1RM estimate accurate at 10 or more reps?+
It gets noticeably worse. The formulas were built from low-rep data, and above about 10 reps the relationship between reps and maximal strength varies a lot between people — endurance-adapted lifters overshoot, pure strength athletes undershoot. Treat estimates from 10+ rep sets as ballpark only.
What percentage of my 1RM should I train at?+
It depends on the goal: roughly 85–100% for maximal strength (1–6 reps), 65–85% for muscle growth (6–15 reps), and under 65% for muscular endurance (15+ reps). Most programs mix these ranges across the week rather than living in one.
How often should I test my actual 1RM?+
Rarely — every 8–16 weeks at most, at the end of a training block, and only for lifts you are technically confident in. True max attempts are fatiguing and carry injury risk. Between tests, estimated 1RM from your working sets tracks progress just as well.
Is my 1RM the same for every exercise?+
No — every lift has its own 1RM, and the rep relationship differs by exercise too. Upper-body lifts and isolation movements typically allow fewer reps at a given percentage than squats or deadlifts, so calibrate each lift with its own recent set.