Badminton String Tension kg vs lbs: How to Convert It

Last checked: August 2026 · Written by the player-led team at Badminton House

Those pairs name equivalent reference forces. They are not new tension recommendations. If you need to choose a setting rather than translate one you already know, use the separate badminton string tension guide and speak with your stringer.

The important habit is simple: keep the original number and unit, calculate with the full factor, then label any rounded result. A bare note such as “11” leaves the stringer guessing whether you meant 11 kgf or 11 lbf—two very different forces.

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What do kg and lbs mean in badminton stringing?

Strictly speaking, kg is a unit of mass. The International Bureau of Weights and Measures defines the kilogram, symbol kg, as the SI unit of mass. Tension is a force, so the precise labels for this job are kilogram-force and pound-force: kgf and lbf.

The shorter language exists in real equipment specifications. Yonex’s current Precision 8.0 stringing-machine page identifies the machine as badminton-capable and expresses its tension range using “lbs” and “kg.” That verifies one common-looking convention; it does not prove that every machine uses the same display, range or settable increment.

For an unambiguous record, write kgf or lbf. If an older ticket says only “kg,” ask whether it meant the machine’s kilogram-force setting. Do not silently treat a kilogram mass value and a kilogram-force value as formally identical units.

The exact conversion relationship

The NIST force-conversion table gives 1 kgf as 9.80665 newtons. Its pound-force footnote gives 1 lbf as exactly 4.4482216152605 newtons under standard gravity. From those definitions, 1 lbf equals exactly 0.45359237 kgf.

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Badminton string tension conversion chart: 8–15 kgf

This chart applies the exact force relationship and shows lbf to one decimal place. The 8–15 kgf span is a lookup range chosen for this article, not a claim that every value suits normal play or that every racket can safely accept it.

Read across one row; do not read down the chart as a progression. A higher row is not an upgrade, an advanced-player badge or permission to exceed the exact racket’s instruction.

The displayed values are rounded. For example, 12 kgf is approximately 26.455471 lbf. That becomes 26.5 lbf to one decimal, but it rounds directly to 26 lbf if a whole-pound result is specifically required. Taking the already rounded 26.5 and rounding it again to 27 would be a double-rounding error.

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How do you translate the tension you remember?

Start by identifying what the remembered number represented. This conversion is for the requested pull written on a machine, receipt or stringing ticket. It is not a way to turn a frequency-app reading or another completed-stringbed measurement into kgf or lbf.

1. Recover the original note if possible. “11.5 kg” on an old stringing ticket is stronger evidence than remembering that the racket felt like “about 25.”
2. Confirm the starting unit. Establish whether kg meant kgf or whether the job was written in lbf.
3. Calculate from the original. Use the full factor rather than converting an already rounded number.
4. Keep both values. Record the original request and the converted result so the stringer can see what was translated.
5. Confirm final rounding. Ask the stringer which increment the actual machine accepts and round the full result once.

Suppose your old ticket says 11.5 kgf. Dividing by 0.45359237 gives approximately 25.353160 lbf. You can write “original request: 11.5 kgf; conversion: 25.353160 lbf; final machine setting to be confirmed.” If the stringer works to one decimal, that displays as 25.4 lbf.

The reverse is just as direct. If the old ticket says 26 lbf, multiply by 0.45359237 to get exactly 11.79340162 kgf, or 11.8 kgf to one decimal. Do not convert it to 12 kgf merely because that looks tidier; 12 kgf is a different force.

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What should you write on the stringing ticket?

A conversion is most useful when the technician can see the request it came from. The following Badminton House hand-off template is practical bookkeeping, not a universal shop form.

If the old job used separate main and cross values, convert each value independently. If it used one value, do not create a mains-to-crosses difference during conversion. Unit arithmetic cannot tell you that an offset is needed or how large it should be.

The frame check remains separate from the arithmetic. Yonex’s badminton safety guidance says to string around the racket’s recommended tension while keeping its original frame shape, and warns that exceeding the recommendation or distorting the shape can cause damage. It also says the recommendation is recorded on each racket.

Read the instruction for the exact racket and variant rather than copying a maximum from a similar name. Our racket maximum-tension guide explains that separate check. A mathematically correct conversion never overrides the frame instruction or a qualified stringer’s refusal to take the job.

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Why can equivalent numbers still feel different?

Unit equivalence is exact: 11.5 kgf and approximately 25.353160 lbf describe the same reference force. What it does not prove is that two stringing jobs, two completed stringbeds or two rackets are otherwise identical.

A technical Cross and Bower tennis-racket experiment separates pull tension from tension after stringing and discusses stress relaxation, frame distortion and friction-related process effects. It is tennis evidence, so its percentages are not a badminton correction formula. Its useful role here is narrower: a reference-pull conversion is not a complete model of the finished racket.

That means conversion alone cannot diagnose why a familiar number feels different after a change of racket, string, stringer, machine or date. If you are trying to reproduce an earlier setup, record those details where known and treat the result as a best-described repeat, not a guarantee.

It also matters when the comparison occurs. An older stringbed is not simply its original ticket expressed in another unit. The separate guide to early string-tension change covers that time-dependent question; the formulas here only translate the stated request.

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Common kg vs lbs conversion questions

Is 1 kg of badminton tension exactly 2.2 lbs?

No. If “kg” means kgf, 1 kgf is approximately 2.20462262185 lbf. Multiplying by 2.2 is a useful estimate, but it is not the full conversion.

Is 10 kg exactly 22 lbs?

No. Ten kgf is approximately 22.046226 lbf. It displays as 22.0 lbf to one decimal and 22 lbf to a whole pound.

Should 12 kg be written as 26 or 26.5 lbs?

The unrounded result is approximately 26.455471 lbf. It becomes 26.5 to one decimal or 26 to a whole pound. State the precision and ask the stringer which increment the machine can actually set.

Does the 8–15 kgf chart show a safe badminton range?

No. It is only the lookup span requested for this conversion guide. Safety and suitability depend on the exact racket instruction and the separate tension-selection decision.

Can I give a stringer the converted number without the unit?

Do not. Write the number with kgf or lbf and retain the original request beside it. The unit is part of the instruction, not optional decoration.