One Rep Max (Mayhew) Calculator
The formula
What the mayhew 1rm tells you
The exponential-decay rep model: percentage of maximum falls as an e-curve with reps, a shape that fits bench-press testing data across dozens of studies.
Calculation: %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ %. Enter your inputs and every substitution is shown below the result.
Reading the result
Where linear models say “every rep costs 3.3 %”, Mayhew says early reps cost more and late reps less — closer to the grind reality.
Rules of thumb: Mayhew 10-rep ≈ 77 % of max for bench-press cohorts
Limitations and best practice
Fitted on college bench tests: squat and deadlift 1RMs come out conservative with it.
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
Why bench-specific?
Better than percentage tables?
Source & methodology
Mayhew et al. 1992–2002 bench test series.
One Rep Max (Mayhew) explained: formula, worked example and honest limits
You are here because you need a specific number, and you want to see how it was produced before you rely on it. There are plenty of pages about One Rep Max (Mayhew); almost none of them show the working. This one does: the formula, every input, a fully computed example, and a sensitivity analysis calculated live from this engine’s own defaults.
What makes One Rep Max (Mayhew) worth calculating is not precision but position: it tells you which side of a threshold you are on, and by how much. A rough figure that settles the direction beats an elaborate one that never commits.
Most confusion about One Rep Max (Mayhew) comes from mixing up the input you control with the input you merely observe. The formula treats them identically, but your decisions should not: one deserves measurement, the other deserves a defensible estimate.
Nothing below is stock text pasted around a number: the worked example computes est. 1RM = 142.7 kg from this tool’s own defaults, 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. Read the sections in order and you will be able to reproduce every figure by hand.
Inside the One Rep Max (Mayhew) calculation: formula and every input
The engine implements a single stated model: %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ %. There is no hidden coefficient and no login-gated precision — the formula printed is the formula executed, which is also what makes the result citable.
Lift (kg) (example value 120) is a quantity rather than a category — precision here is cheap and worth having. Use the same conditions each time (same scale, same time of day) so that changes in the output reflect real change.
Reps completed (example value 5) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. If you are unsure what belongs in this field, look at the printed steps: the substitution shows exactly how the engine uses it.
One Rep Max (Mayhew) with real numbers, step by step
Abstract formulas are hard to trust, so here is the complete substitution using the default inputs, written the way an examiner would want it. Starting figures: Lift (kg), Reps completed. The computed est. 1RM comes out at 142.7 kg, which the interpretation band labels “Mayhew’s exponential bench-mark curve puts this set at 84.1 % of max → 142.7 kg; the model was fitted on bench-press test data, so it is the most honest bench estimate of the family”.
- 52.26 + 41.9·e^(−0.055 × 5) = 84.1 %
- 1RM = 120 ÷ 0.841 = 142.7 kg
- The e-term decays ~5 % per added rep
% of max used — 84.1%. If your inputs change, this is usually the first companion figure to move.
Epley comparison — 140.0 kg. This is the number experienced users quote when the headline alone would mislead.
12RM at this model — 105.5 kg. Read next to the headline, this is the figure that shows the shape of the trade-off.
Curve shape — asymptote ~52 % as reps explode. This is the number experienced users quote when the headline alone would mislead.
Re-running with your own figures is instant; re-running by hand once is the best way to know the tool is telling you the truth.
Scenario table: One Rep Max (Mayhew) at ±10 % and ±20 % of the key input
Single-point answers invite false confidence, so the same engine was run across a band around the input that matters most here. Each row is a full recalculation of One Rep Max (Mayhew), not an interpolation.
| Lift setting | Est. 1RM |
|---|---|
| 80 % of the example value | 114.2 kg |
| 90 % of the example value | 128.4 kg |
| example inputs | 142.7 kg |
| 110 % of the example value | 157.0 kg |
| 120 % of the example value | 171.3 kg |
That spread — 114.2 kg at the low end, 171.3 kg at the high — is what a careful read of One Rep Max (Mayhew) 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.
Sensitivity: which inputs change One Rep Max (Mayhew) the most
Generic advice says “it depends on your inputs”; this section says exactly how much. Each field was perturbed by ±10 % in isolation and the est. 1RM recomputed, so the ranking below is measured rather than asserted. Read it as a map of where One Rep Max (Mayhew) is fragile — drawn for the example inputs, which is the map you want when deciding what to measure carefully.
- Nudge Lift by ±10 % and One Rep Max (Mayhew) lands between 128.4 kg and 157.0 kg (sensitivity ≈10.0 %)
- Reps completed +10 % → One Rep Max (Mayhew) = 144.2 kg · −10 % → 141.2 kg (the est. 1RM shifts ≈1.0 %)
Lift is the dominant lever here: ten percent either way moves the result by about 10.0 %, from 128.4 kg to 157.0 kg. That is where a careless figure does the most damage, so check it against a source, and treat Reps completed as the second priority (≈1.0 % per ten percent). The rest of the inputs earn only a rounding-error of attention, and that asymmetry is the practical payoff of measuring rather than asserting.
Interpreting the One Rep Max (Mayhew) verdict
A number on its own is trivia; a number against a range is intelligence. The verdict attached to the default calculation — “Mayhew’s exponential bench-mark curve puts this set at 84.1 % of max → 142.7 kg; the model was fitted on bench-press test data, so it is the most honest bench estimate of the family” — is one band on a ladder your own figure may sit somewhere else on. How much of that band is luck? On Lift alone ten percent either way covers 128.4 kg to 157.0 kg. The practical reading rules: read the band as a starting hypothesis, then test it: change the two dominant inputs by ten percent and see whether the verdict survives. Verdicts that survive stress are the ones worth acting on.
In Fitness & Sports, One Rep Max (Mayhew) is one instrument in an orchestra: on its own it is a number, next to % of max used and Epley comparison it becomes a diagnosis. The tools linked above exist so the headline never has to carry that weight alone.
The errors that quietly break a One Rep Max (Mayhew) figure
Fitted on college bench tests: squat and deadlift 1RMs come out conservative with it. 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.
Treating the example inputs as a recommendation. They are a demonstration of the mechanism — a decision-grade One Rep Max (Mayhew) begins the moment your own figures replace them.
Attention is also misallocated between fields. Having measured this engine, we can say where it belongs: Lift first, everything else second.
Another is comparing across contexts: a One Rep Max (Mayhew) computed with one set of conventions should never be lined up against a figure computed with another. Check the inputs behind both before ranking them.
One Rep Max (Mayhew) verification checklist
- Compare the output against one published benchmark or a colleague’s independent estimate.
- 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 %.
- Note the date and the inputs beside the number so the figure can be audited later.
- Check that every field the formula needs actually arrived from a document, not from recollection.
- Repeat the ±10 % test on the inputs that matter and see whether the decision — not just the number — still holds.
A routine for decision-grade One Rep Max (Mayhew)
Using a calculator well sounds trivial, but the difference between a decision-grade figure and a throwaway one lives entirely in the routine. The routine for One Rep Max (Mayhew) takes a minute to learn and applies to every input above.
Step 1 — gather before you type. One Rep Max (Mayhew) 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. Re-running a number costs seconds; retracting a decision costs considerably more.
Step 2 — start from the case you can defend. Enter pessimistic-but-honest figures first; the optimistic run is a ceiling, not a plan. A conclusion that holds on conservative inputs holds everywhere. Write the assumptions in the same file as the result, and future arguments take minutes instead of meetings.
Step 3 — change one input at a time. Nudge a single field by ten percent, watch the headline and its companions move, then undo it. Two or three fields will dominate — the sensitivity table above already ranks them for this engine. Note the assumption you are least sure about; that is where the real risk lives.
Step 4 — run the scenario trio. Expected, pessimistic, optimistic. The gap between pessimistic and expected is the number to plan against; the optimistic result is useful only as a ceiling. If a result feels obviously right, that is the moment to check the inputs hardest.
Step 5 — write the one-line memo. “Est. 1RM = 142.7 kg on this date, from these inputs.” That line is the entire deliverable; everything else on this page is how you earned the right to write it. Compare the calculation to the rough guess you arrived with, and ask why they differ.
Who actually uses One Rep Max (Mayhew) — and when
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. Say the answer out loud before you save it; if it sounds wrong, the model did not change, your understanding did.
Professionals in Strength Training use this style of calculation as a screening filter before spending real money or effort: a quick One Rep Max (Mayhew) check eliminates weak options in minutes, and the survivors earn the deeper, slower analysis. Re-running a number costs seconds; retracting a decision costs considerably more.
There is a personal-administration use people overlook: periodic self-checking. One Rep Max (Mayhew) quietly drifts as life changes — rates move, bodies change, costs compound — and re-running it a few times a year catches drift while correction is still cheap. When two sources disagree, it is almost never the arithmetic that differs.
Quick answers: what searchers ask about One Rep Max (Mayhew)
What affects One Rep Max (Mayhew) the most?
Measured on this engine, Lift is the dominant lever: moving it ±10 % shifts the est. 1RM across 128.4 kg to 157.0 kg — about 10.0 % of the headline, with Reps completed next at ≈1.0 %. The ranked list in the sensitivity section is computed live, not asserted from a template.
Which matters more: reps completed or lift?
By the numbers, Lift: a ten-percent change in it moves the result ≈10.0 %, versus ≈1.0 % for Reps completed. Spend your measuring effort in that order — precision on the weaker lever buys almost nothing.
What is a typical One Rep Max (Mayhew)?
With the example inputs on this page the result is 142.7 kg, labelled “Mayhew’s exponential bench-mark curve puts this set at 84.1 % of max → 142.7 kg; the model was fitted on bench-press test data, so it is the most honest bench estimate of the family”. “Typical” varies with situation, which is why every result here ships with its verdict band and its sensitivity list: they turn one figure into a range you can locate yourself inside.
How do I calculate One Rep Max (Mayhew) by hand?
Use the stated model — %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ % — and substitute in the order the tool prints (it starts from 52.26 + 41.9·e^(−0.055 × 5) = 84.1 %). On the example inputs the hand route lands on 142.7 kg, exactly what the calculator shows. A spreadsheet reproduces it in two or three cells; doing it once by hand is what makes the automated answer trustworthy.
What happens to One Rep Max (Mayhew) if lift changes by 10 %?
The engine was re-run with that field moved by ten percent while everything else stayed fixed: the est. 1RM goes across 128.4 kg to 157.0 kg, a swing of roughly 10.0 % around the 142.7 kg baseline. That ratio is the practical definition of how much this input matters.
Is the One Rep Max (Mayhew) result of 142.7 kg good or bad?
Neither, on its own — the label “Mayhew’s exponential bench-mark curve puts this set at 84.1 % of max → 142.7 kg; the model was fitted on bench-press test data, so it is the most honest bench estimate of the family” is the band this figure falls in for the example inputs, and your own inputs will place you elsewhere on the same ladder. Judge the number against your history and your alternatives, and remember that a ten-percent error in Lift alone moves it by ≈10.0 %.
What affects One Rep Max (Mayhew) the most?
Sensitivity depends on where you start, but the inputs Lift (kg) and Reps completed typically move One Rep Max (Mayhew) further than the rest because they enter the formula multiplicatively. If you can only measure two things well, measure those and hold the others at conservative defaults.
How do I calculate One Rep Max (Mayhew) manually?
Write down the inputs, then follow the printed steps in order — %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ %. A spreadsheet replicates it with two or three cells. The manual route is worth doing once to build intuition; after that the calculator saves time and eliminates transcription slips.
Why bench-specific?
The 52.26/41.9 constants came from large bench-press samples; muscle-group constants differ.
Better than percentage tables?
It is a continuous percentage table — same information, no page-turning.
Does this One Rep Max (Mayhew) 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.
Glossary for One Rep Max (Mayhew)
- % of max used
- 84.1% on the example inputs — a companion figure printed beside the headline of One Rep Max (Mayhew) so that no result is read in isolation.
- Epley comparison
- 140.0 kg in the default One Rep Max (Mayhew) calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- 12RM at this model
- 105.5 kg for the One Rep Max (Mayhew) worked case; it sits next to the main result because it carries context the headline leaves out.
- Est. 1RM
- The primary output of this tool: 142.7 kg for the default inputs, computed exactly from %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ %.
- Worked example
- Every substitution in order, from the example inputs to 142.7 kg — the audit trail for the headline figure.
- Verdict band
- The plain-language label — here “Mayhew’s exponential bench-mark curve puts this set at 84.1 % of max → 142.7 kg; the model was fitted on bench-press test data, so it is the most honest bench estimate of the family” — mapping the computed figure onto experience-based ranges for Fitness & Sports.
- Sensitivity (±10 %)
- How far the One Rep Max (Mayhew) moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
The provenance of this One Rep Max (Mayhew) calculation
The model is published arithmetic implemented exactly as written: %1RM = 52.26 + 41.9·e^(−0.055·r); 1RM = w ÷ %. Source of record: Mayhew et al. 1992–2002 bench test series. Specialist software layers extra coefficients on top of the same algebra; none are hidden here, and that transparency is what makes a disagreement traceable to a specific input instead of a black box.
Treat the output as a precise answer to the question you typed: exact arithmetic, transparent formula, published source, no hidden rounding. Nothing is smoothed, weighted or adjusted behind the scenes; where judgement enters, this page says so and names the input responsible.
Turning this One Rep Max (Mayhew) into a decision
Save the number together with its inputs and today’s date; a One Rep Max (Mayhew) 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.