Quad:Ham Ratio Calculator
The formula
What the hamstring balance tells you
The hamstring-to-quadriceps strength ratio — the single most-cited muscle-balance number in sprint and ACL injury research.
Calculation: H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat. Enter your inputs and every substitution is shown below the result.
Reading the result
Conventional curl:squat near 0.6–0.65; below that the hamstring is a spectator when the quad is a star, and sprints do not forgive spectators.
Rules of thumb: Elite sprinters maintain conventional 0.6–0.8; injured side typically >0.15 off
Limitations and best practice
Isolation-machine ratios miss co-contraction; functional H:Q (Nordsboard/AssisTech) predicts strains better.
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
Which exercises for the proxies?
Nordic hamstring vs curls?
Source & methodology
Dauty/Ronai H:Q literature; Orchard ratings.
How Quad:Ham Ratio works — and what your result really means
This page was written for one job: turning your own inputs into a defensible figure, with the working shown. Searchers land on a Quad:Ham Ratio 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.
There is a habit that separates people who get useful answers from Strength Training numbers: they decide what question the figure answers before they compute it. Quad:Ham Ratio answers “H:Q ratio?” — and nothing else, which is precisely why the result is trustworthy.
The useful way to hold Quad:Ham Ratio is as a ratio with a story attached: H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat says how the parts combine, and the 0.38 figure above is simply that sentence written in numbers. Everything that follows unpacks one clause of the sentence at a time.
Every figure in the prose is generated by the engine rather than written beside it — the worked example resolves to h:Q ratio = 0.38 on the default inputs, and the sensitivity section ranks the inputs that move the result — Quad strength proxy (kg, e.g. leg extension 1RM) first, at ≈11.1 % 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.
How Quad:Ham Ratio is computed, line by line
The engine implements a single stated model: H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat. 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.
Quad strength proxy (kg, e.g. leg extension 1RM) (example value 74) is a plain measured quantity — the unit shown in the label is the unit the formula expects. Weigh rather than estimate where you can — this field usually enters the formula multiplicatively.
Hamstring strength proxy (kg, curl 1RM) (example value 28) is a measured number in the unit named by the label; the formula does not convert for you. Weigh rather than estimate where you can — this field usually enters the formula multiplicatively.
Interpretation (example value Conventional H:Q (ham/quad)) is a branching choice rather than a figure you measure; the per-option effects are computed below. Replace the example with the figure from your own records — the tool recomputes instantly and the printed steps follow your numbers.
A fully worked Quad:Ham Ratio example
The tool prints its own working; this is the same arithmetic on the example values, reproduced so you can follow it by hand. Starting figures: Quad strength proxy (kg, e.g. leg extension 1RM), Hamstring strength proxy (kg, curl 1RM), Interpretation. The computed h:Q ratio comes out at 0.38, which the interpretation band labels “The hamstrings carry 38 % of quad strength; below 0.60 is the classic sprint-injury signature — here the gap to 64 % is 19.4 kg of curl to close”.
- H:Q = 28 ÷ 74 = 0.38
- Target 0.64 → shortfall 19.4 kg
- Or drop quad load — but the answer is curls and Nordics
Inverse Q:H — 2.64. Read next to the headline, this is the figure that shows the shape of the trade-off.
Curl load to close gap — 19.4 kg. Compare it against the main result of 0.38 before drawing conclusions.
Nordic caveat — eccential strength is the better predictor. Compare it against the main result of 0.38 before drawing conclusions.
Re-test — add eccentrics, re-test in 6 weeks. Compare it against the main result of 0.38 before drawing conclusions.
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: Quad:Ham Ratio at ±10 % and ±20 % of the key input
The honest version of any estimate is a corridor, and this one is cheap to produce: Quad:Ham Ratio was recomputed at 5 points along the dominant input, with every other field left untouched.
| Quad strength proxy (kg, e.g. leg extension 1RM) setting | H:Q ratio |
|---|---|
| 80 % of the example value | 0.47 |
| 90 % of the example value | 0.42 |
| example inputs | 0.38 |
| 110 % of the example value | 0.34 |
| 120 % of the example value | 0.32 |
Across 5 settings of Quad strength proxy (kg, e.g. leg extension 1RM), the result spans 0.32 to 0.47. A decision that only works at one row of this table is a decision waiting for an input to move. Reproduce it in the form above by editing Quad strength proxy (kg, e.g. leg extension 1RM) alone; the substitution steps will follow your figures exactly.
What actually moves your Quad:Ham Ratio
This list was computed for this specific engine just now: each numeric input was nudged ±10 % while every other field held its example value, and the h:Q ratio was recalculated from scratch. Read it as a map of where Quad:Ham Ratio is fragile — drawn for the example inputs, which is the map you want when deciding what to measure carefully.
- Nudge Quad strength proxy (kg, e.g. leg extension 1RM) by ±10 % and Quad:Ham Ratio lands between 0.34 and 0.42 (sensitivity ≈11.1 %)
- Nudge Hamstring strength proxy by ±10 % and Quad:Ham Ratio lands between 0.34 and 0.42 (sensitivity ≈10.0 %)
Quad strength proxy (kg, e.g. leg extension 1RM) is the dominant lever here: ten percent either way moves the result by about 11.1 %, from 0.34 to 0.42. Measure that input from a document rather than from memory, and treat Hamstring strength proxy as the second priority (≈10.0 % per ten percent). The remaining fields can sit at safe defaults without materially changing the answer — knowing which is which is what separates a careful calculation from an anxious one.
Reading the result: bands, zones and thresholds
The value above only becomes useful the moment you know what it is being measured against. On the example inputs the band reads “The hamstrings carry 38 % of quad strength; below 0.60 is the classic sprint-injury signature — here the gap to 64 % is 19.4 kg of curl to close”; your own figures place you on a different rung of the same ladder. The sensitivity list shows how far a modest input error moves you along that ladder: for Quad strength proxy (kg, e.g. leg extension 1RM), ±10 % covers 0.34 to 0.42. The practical reading rules: compare against your own history before comparing against other people; treat band boundaries as zones, not walls — one point on the wrong side of a threshold rarely changes a real outcome; and when a companion output contradicts the headline, believe the pair.
Where Quad:Ham Ratio sits next to similar measures: this tool answers “how much is the Quad:Ham Ratio”, 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.
The errors that quietly break a Quad:Ham Ratio figure
Isolation-machine ratios miss co-contraction; functional H:Q (Nordsboard/AssisTech) predicts strains better. 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.
Copying a single headline number without checking the companion outputs. The tool reports Inverse Q:H, Curl load to close gap and Nordic caveat alongside the main result precisely because Quad:Ham Ratio in isolation misleads — the secondary columns are where outliers and trade-offs show up.
This model has its own particular trap: Quad strength proxy (kg, e.g. leg extension 1RM) carries ≈11.1 % of the response per ten percent of error, so effort spent elsewhere is largely decorative.
Another is comparing across contexts: a Quad:Ham Ratio 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.
Before you trust your Quad:Ham Ratio: a short checklist
- Compare the result with one independent method or published benchmark.
- Note the date and the inputs beside the number so the figure can be audited later.
- Put Quad strength proxy (kg, e.g. leg extension 1RM) under a magnifier; the sensitivity table above is the reason why.
- Confirm the example values are plausible for your own situation before replacing them.
- Recompute once with the dominant input deliberately set low, and see whether the decision changes.
- Run the ±10 % stress on the top two levers and check that your conclusion survives both.
How to use the Quad:Ham Ratio tool properly
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 Quad:Ham Ratio takes a minute to learn and applies to every input above.
Step 1 — gather before you type. Quad:Ham Ratio depends on quad strength proxy (kg, e.g. leg extension 1rm), hamstring strength proxy (kg, curl 1rm), interpretation. 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. Numbers are cheap to produce and expensive to retract; the extra minute is the cheapest insurance available.
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. Half of a good calculation is knowing which input you would hate to be wrong about.
Step 3 — play with the inputs on purpose. Ten percent up, ten percent down, one field at a time. Within a few minutes you will know this calculation better than most people who quote its results. The inputs are the part of the work that nobody else can do for you.
Step 4 — ask what would have to be true. Take the result you want and work backwards through the inputs until you find the assumption that produces it; then decide honestly whether that assumption is defensible. Comparisons are cheap: run the identical calculation for the alternative and look at the gap.
Step 5 — schedule the next run. In Fitness & Sports the inputs drift quietly. Put a reminder a quarter out, re-enter the same fields, and read the change rather than the level. One decimal place more than your data supports is one decimal place of fiction.
Who actually uses Quad:Ham Ratio — 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. Compare the calculation to the rough guess you arrived with, and ask why they differ.
Professionals in Strength Training use this style of calculation as a screening filter before spending real money or effort: a quick Quad:Ham Ratio check eliminates weak options in minutes, and the survivors earn the deeper, slower analysis. The point of transparency is that a reader can disagree with a specific line rather than with you.
Re-running this page costs nothing and catches the slow drifts that never announce themselves. In Fitness & Sports the expensive mistakes are rarely sudden; they are small changes in Quad strength proxy (kg, e.g. leg extension 1RM) that nobody recalculated for a year. The point of transparency is that a reader can disagree with a specific line rather than with you.
People also ask about Quad:Ham Ratio
What affects Quad:Ham Ratio the most?
Quad:Ham Ratio is driven above all by Quad strength proxy (kg, e.g. leg extension 1RM). Perturbing only that field by ten percent either way produced 0.34 against the 0.38 baseline — a ≈11.1 % response, while Hamstring strength proxy manages ≈10.0 %.
Which matters more: hamstring strength proxy or quad strength proxy (kg, e.g. leg extension 1rm)?
By the numbers, Quad strength proxy (kg, e.g. leg extension 1RM): a ten-percent change in it moves the result ≈11.1 %, versus ≈10.0 % for Hamstring strength proxy. Spend your measuring effort in that order — precision on the weaker lever buys almost nothing.
What is a typical Quad:Ham Ratio?
On the worked example above Quad:Ham Ratio comes out at 0.38. Treat that as one point on a distribution rather than a norm: the bands, the companion outputs and the sensitivity ranking tell you how wide the plausible range really is.
How do I calculate Quad:Ham Ratio by hand?
Use the stated model — H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat — and substitute in the order the tool prints (it starts from H:Q = 28 ÷ 74 = 0.38). On the example inputs the hand route lands on 0.38, 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 Quad:Ham Ratio if quad strength proxy (kg, e.g. leg extension 1rm) changes by 10 %?
On these inputs a ±10 % change in quad strength proxy (kg, e.g. leg extension 1rm) takes Quad:Ham Ratio to 0.34 against the 0.38 example — around 11.1 % of the headline. The same test on every other field is in the sensitivity section.
Is the Quad:Ham Ratio result of 0.38 good or bad?
The tool answers “what”, not “whether”: 0.38 carries the verdict “The hamstrings carry 38 % of quad strength; below 0.60 is the classic sprint-injury signature — here the gap to 64 % is 19.4 kg of curl to close” for the default case, which is a starting interpretation rather than a verdict on your situation. Re-run with your own figures and compare the bands.
How often do I recheck Quad:Ham Ratio?
Whenever Quad strength proxy (kg, e.g. leg extension 1RM) changes materially, or on a deliberate block cycle (4–8 weeks is standard practice). A stale Quad:Ham Ratio under-programs strong athletes and over-programs tired ones.
Can Quad:Ham Ratio be negative or empty?
Yes, and that is informative rather than broken: a negative Quad:Ham Ratio usually means the inputs encode an outflow or a shortfall, and the verdict band above labels exactly that situation instead of hiding it.
Which exercises for the proxies?
Seated curl and leg-extension 1RMs are the conventional pair; report the same pair every re-test.
Nordic hamstring vs curls?
Nordics add eccentric lengthening strength — the exact quality the late-swing hamstring needs.
Is my data private on this page?
Yes — computation happens locally in your browser, with no account, no tracking of your inputs and nothing sent to a server. The printed formula is the whole story of what happens to your figures.
The vocabulary of Quad:Ham Ratio
- Inverse Q:H
- 2.64 on the example inputs — a companion figure printed beside the headline of Quad:Ham Ratio so that no result is read in isolation.
- Curl load to close gap
- 19.4 kg for the Quad:Ham Ratio worked case; it sits next to the main result because it carries context the headline leaves out.
- Nordic caveat
- eccential strength is the better predictor for the Quad:Ham Ratio worked case; it sits next to the main result because it carries context the headline leaves out.
- H:Q ratio
- The primary output of this tool: 0.38 for the default inputs, computed exactly from H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat.
- Worked example
- The calculation written out in full so that nothing on this page has to be taken on trust.
- Verdict band
- The interpretation attached to a result (“The hamstrings carry 38 % of quad strength; below 0.60 is the classic sprint-injury signature — here the gap to 64 % is 19.4 kg of curl to close” on these inputs), which turns a bare number into a position on a scale.
- Sensitivity (±10 %)
- How far the Quad:Ham Ratio 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 Quad:Ham Ratio calculation
The model is published arithmetic implemented exactly as written: H:Q = ham ÷ quad; injury-risk band ≈ 0.60 conventional curl:squat. Source of record: Dauty/Ronai H:Q literature; Orchard ratings. 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.
What to do with your Quad:Ham Ratio next
Re-run the calculation with your own figures, stress the two most sensitive inputs by ±10 %, and only then act on the result.
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.