One Rep Max (Brzycki) Calculator
The formula
What the brzycki 1rm tells you
The curved alternative: percentage-of-max falls one thirty-sixth per rep, so high-rep sets inflate the estimate more than Epley’s line does.
Calculation: 1RM = w × 36 / (37 − r). Enter your inputs and every substitution is shown below the result.
Reading the result
Brzycki’s 10-rep ≈ 74.5 % of max is the number sports programs still standardise on; the curve is its fingerprint.
Rules of thumb: Brzycki and Epley diverge ~4 % between reps 6 and 10
Limitations and best practice
Past ~12 reps the hyperbola overshoots violently — Brzycki is a 1–10 rep tool in honest hands.
This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Frequently asked questions
Is 10RM 75 % or 74 %?
Which formula is most accurate?
Source & methodology
Brzycki 1997; NSCA rep-percentage tradition.
One Rep Max (Brzycki) explained: formula, worked example and honest limits
This page was written for one job: turning your own inputs into a defensible figure, with the working shown. Searchers land on a One Rep Max (Brzycki) page for three reasons — to plan, to compare options, and to check that somebody else’s arithmetic is honest. This tool serves all three, and everything after the calculator explains the model instead of hiding it.
The number itself is the easy part. What takes judgement is knowing which inputs are facts in your situation and which are guesses wearing a decimal point — a distinction this page makes explicit for every field above.
Individual variation is large here: limb proportions, fibre mix and history all shift how a population-average One Rep Max (Brzycki) maps to you. Use it as a starting prescription, then let performance feedback over weeks tune it.
What makes a calculation page trustworthy is that its copy is derived from its own arithmetic: here est. 1RM = 185.8 kg, recomputed every time a field changes, and the sensitivity section ranks the inputs that move the result — Lift first, at ≈10.0 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.
Inside the One Rep Max (Brzycki) calculation: formula and every input
Here is the complete model this tool runs — 1RM = w × 36 / (37 − r) — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.
Lift (kg) (example value 160) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. Stay in one unit system top to bottom; conversion rounding is where small errors enter.
Reps completed (example value 6) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. The example value is there to demonstrate the mechanics, not to describe your situation — overwrite it.
A fully worked One Rep Max (Brzycki) example
Rather than describe the calculation, here it is end to end — every substitution in order, starting from the inputs above. Starting figures: Lift (kg), Reps completed. The endpoint of that chain is 185.8 kg of est. 1RM, sitting in the “Brzycki’s hyperbola turns 160 × 6 into 185.8 kg — it grows faster than Epley at mid rep counts, which is why the pair bracket the truth rather than agree” band.
- 36 ÷ (37 − 6) = 1.1613
- × 160 kg = 185.8 kg
- Inverse form: %1RM = 36/(37−reps) → 116.1 %
Epley comparison — 192.0 kg. If your inputs change, this is usually the first companion figure to move.
% of estimated max — 86.1%. Compare it against the main result of 185.8 kg before drawing conclusions.
5RM at this curve — 165.2 kg. If your inputs change, this is usually the first companion figure to move.
Rep ceiling — formula breaks at 36 reps. Compare it against the main result of 185.8 kg before drawing conclusions.
Overwrite any input above and every line of this example updates with it — the substitution is live, not a screenshot of somebody else’s numbers.
Scenario table: One Rep Max (Brzycki) at ±10 % and ±20 % of the key input
The honest version of any estimate is a corridor, and this one is cheap to produce: One Rep Max (Brzycki) was recomputed at 5 points along the dominant input, with every other field left untouched.
| Lift setting | Est. 1RM |
|---|---|
| 80 % of the example value | 148.6 kg |
| 90 % of the example value | 167.2 kg |
| example inputs | 185.8 kg |
| 110 % of the example value | 204.4 kg |
| 120 % of the example value | 223.0 kg |
That spread — 148.6 kg at the low end, 223.0 kg at the high — is what a careful read of One Rep Max (Brzycki) looks like: a band you can state out loud, with the reason for each edge. Reproduce it in the form above by editing Lift alone; the substitution steps will follow your figures exactly.
What actually moves your One Rep Max (Brzycki)
Nobody should have to guess which input matters. The engine was re-run once per field below — ten percent up, ten percent down, everything else frozen — and the results ranked by how far they moved the est. 1RM. It is the fastest honest answer to “what matters most in One Rep Max (Brzycki)?” — and it is specific to these defaults, because sensitivity moves with the starting point.
- Lift +10 % → One Rep Max (Brzycki) = 204.4 kg · −10 % → 167.2 kg (the est. 1RM shifts ≈10.0 %)
- Nudge Reps completed by ±10 % and One Rep Max (Brzycki) lands between 182.3 kg and 189.5 kg (sensitivity ≈2.0 %)
Lift is the dominant lever here: ten percent either way moves the result by about 10.0 %, from 167.2 kg to 204.4 kg. Spend your verification effort there first, and treat Reps completed as the second priority (≈2.0 % per ten percent). Everything below that can stay approximate, which is a licence to stop chasing data that would not change the decision.
Interpreting the One Rep Max (Brzycki) verdict
The value above only becomes useful the moment you know what it is being measured against. On the example inputs the band reads “Brzycki’s hyperbola turns 160 × 6 into 185.8 kg — it grows faster than Epley at mid rep counts, which is why the pair bracket the truth rather than agree”; your own figures place you on a different rung of the same ladder. Before treating the band as fact, note its width: ten percent either way on Lift already spans 167.2 kg to 204.4 kg. The practical reading rules: ask what would have to change to move you one band. If the answer is “a small, plausible input difference”, the band itself is not the finding — the uncertainty is.
Where One Rep Max (Brzycki) sits next to similar measures: this tool answers “how much is the One Rep Max (Brzycki)”, while the related calculators answer “what do I do about it”. Reading the result alone tends to over-weight a single snapshot; pairing it with the companion tools above turns the number into a decision.
How people get One Rep Max (Brzycki) wrong
Past ~12 reps the hyperbola overshoots violently — Brzycki is a 1–10 rep tool in honest hands. This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Comparing a One Rep Max (Brzycki) computed here with a figure from another source that uses different conventions. Same name, different denominator — the disagreement is usually in the definitions, not the data.
One mistake is specific to this engine: assuming every input matters equally. The computation above shows Lift dominating — a careful figure there beats false precision everywhere else.
A final trap is presentation: reporting One Rep Max (Brzycki) to more decimal places than the inputs support. The tool prints what the arithmetic gives; you should quote only what your least precise field justifies.
Before you trust your One Rep Max (Brzycki): a short checklist
- Record the date and the inputs alongside the number so future-you knows what was assumed.
- Verify each input against its original source document, not memory.
- Re-verify Lift against a source document — ten percent of error there moves the headline by ≈10.0 %.
- Check that every field the formula needs actually arrived from a document, not from recollection.
- Confirm the example values are plausible for your own situation before replacing them.
- Repeat the ±10 % test on the inputs that matter and see whether the decision — not just the number — still holds.
Five steps from raw inputs to a figure you can defend
The tool does the arithmetic; the routine below is what makes the arithmetic trustworthy. Five steps, a minute total — and afterwards you will know not just what the number is, but which assumption produced it.
Step 1 — gather before you type. One Rep Max (Brzycki) depends on lift (kg), reps completed. Collect them from a source document — a statement, a report, an invoice, a log — rather than from memory, because recalled inputs are the single largest cause of wrong results. The point of transparency is that a reader can disagree with a specific line rather than with you.
Step 2 — baseline before exploration. Get one defensible Est. 1RM on screen before you start nudging numbers. Without a baseline, every variation looks interesting and none of them means anything. Estimates improve most when the worst case is written down in ink.
Step 3 — measure what deserves measuring. The ranked levers above tell you where a careful figure pays off. Everything else can stay approximate, which is a licence to stop hunting for data you do not need. A figure nobody can reproduce is a figure nobody will act on twice.
Step 4 — stress before you commit. A decision that survives a ten-percent squeeze on its two biggest inputs needs no luck to be sound. One that does not survive is a decision about hope, not about arithmetic. A calculation you cannot explain to somebody else is a calculation you cannot defend.
Step 5 — save the story with the figure. A number without its inputs and its date is unusable within a quarter. Record 185.8 kg, the assumptions behind it, and today’s date; your future self will be auditing a stranger’s arithmetic. Suspiciously tidy answers deserve the same scrutiny as untidy ones.
Where One Rep Max (Brzycki) matters in practice
In Strength Training the figure computed here is usually the first one somebody asks to see. Having it — with the formula behind it — changes your position in the conversation from participant to reference. If a result feels obviously right, that is the moment to check the inputs hardest.
The companion outputs — Epley comparison and % of estimated max — exist for the second stage of that screen: the headline sizes the prize, while the companions describe the trade-off you are accepting to get it. If the answer changes your behaviour, it deserves a second run with different assumptions.
Nothing here is stored or transmitted, so the habit of checking is free: open the page, re-enter current figures, compare with the number you saved last time. Suspiciously tidy answers deserve the same scrutiny as untidy ones.
The questions that come up most about One Rep Max (Brzycki)
What affects One Rep Max (Brzycki) the most?
The short answer: Lift. The longer answer is the sensitivity table on this page, where every numeric input was probed by ten percent and the est. 1RM recalculated — Lift moved it furthest, by roughly 10.0 % (167.2 kg to 204.4 kg).
Which matters more: reps completed or lift?
Lift, by a factor of about 5.1. Concretely: ten percent on Lift is worth ≈10.0 % of One Rep Max (Brzycki), the same nudge on Reps completed only ≈2.0 %. That ranking is re-computed for each page from that page’s own defaults.
What is a typical One Rep Max (Brzycki)?
There is no honest universal average for One Rep Max (Brzycki), but there is a reference point: the defaults on this page produce 185.8 kg (Brzycki’s hyperbola turns 160 × 6 into 185.8 kg — it grows faster than Epley at mid rep counts, which is why the pair bracket the truth rather than agree). Replace the inputs with your own and compare — that comparison is the useful meaning of “typical”.
How do I calculate One Rep Max (Brzycki) by hand?
Three steps: write the formula (1RM = w × 36 / (37 − r)), insert your values, and simplify. The worked example section shows exactly that chain for the default inputs; replicating it once on paper teaches you more about One Rep Max (Brzycki) than any number of calculator runs.
What happens to One Rep Max (Brzycki) if lift changes by 10 %?
Try it in the form above and the printed substitution will follow you; the pre-computed answer for the defaults is 167.2 kg to 204.4 kg across the ten-percent probe, i.e. ≈10.0 % sensitivity on the est. 1RM.
Is the One Rep Max (Brzycki) result of 185.8 kg good or bad?
Good and bad are comparisons, so the honest test is three questions: where does your own One Rep Max (Brzycki) sit against the 185.8 kg reference above, how far would a plausible input error move it (≈10.0 % per ten percent on Lift), and what does the alternative option compute to?
Is One Rep Max (Brzycki) individualized?
Partly — the tool is mechanical on the inputs you provide (Lift (kg), Reps completed); what varies person-to-person is the response. Start at the computed 185.8 kg, adjust by results within a few sessions.
How often should I check One Rep Max (Brzycki)?
Whenever an input changes by more than a few percent, and otherwise on the rhythm of your decisions — before a purchase, a review, a renewal. One Rep Max (Brzycki) is a snapshot, not a subscription; stale snapshots are the most common silent error in Fitness & Sports planning.
Is 10RM 75 % or 74 %?
Brzycki gives 74.5 %; NSCA tables give 75 % — the difference is rounding, the convention matters more.
Which formula is most accurate?
Meta-analyses show no universal winner; within-subject consistency with one formula beats switching.
Does this One Rep Max (Brzycki) tool store my numbers?
No. The entire calculation runs in your browser session; nothing entered above is transmitted or saved, which is the correct behaviour for sensitive Fitness & Sports figures and the reason you can re-run this page as often as you like.
The vocabulary of One Rep Max (Brzycki)
- Epley comparison
- 192.0 kg for the One Rep Max (Brzycki) worked case; it sits next to the main result because it carries context the headline leaves out.
- % of estimated max
- 86.1% in the default One Rep Max (Brzycki) calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- 5RM at this curve
- 165.2 kg on the example inputs — a companion figure printed beside the headline of One Rep Max (Brzycki) so that no result is read in isolation.
- Est. 1RM
- The primary output of this tool: 185.8 kg for the default inputs, computed exactly from 1RM = w × 36 / (37 − r).
- Worked example
- The step-by-step substitution printed above, so the arithmetic can be re-derived by hand or in a spreadsheet.
- Verdict band
- The interpretation attached to a result (“Brzycki’s hyperbola turns 160 × 6 into 185.8 kg — it grows faster than Epley at mid rep counts, which is why the pair bracket the truth rather than agree” on these inputs), which turns a bare number into a position on a scale.
- Sensitivity (±10 %)
- How far the One Rep Max (Brzycki) moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Methodology, sources and limits
Everything above runs on one stated formula, applied without hidden coefficients: 1RM = w × 36 / (37 − r). Source of record: Brzycki 1997; NSCA rep-percentage tradition. Any other implementation of this model should return the same figure for the same inputs. If one does not, the difference is in its assumptions — which this page prints and that one probably does not.
Nothing here replaces a qualified professional, and nothing here is approximate either — the arithmetic is exact, and the honesty is in the inputs you supply. The sensitivity table above is part of that promise rather than a bonus: it lets you see how much of the result depends on how carefully you measured.
Turning this One Rep Max (Brzycki) into a decision
Save the number together with its inputs and today’s date; a One Rep Max (Brzycki) figure without context is unusable the moment an input changes.
The audience here is people who need one trustworthy number before their next decision. Everything you need to defend the result — formula, substitution, sensitivity, source — is printed above, so the only remaining variable is the honesty of your inputs.