Free tools/Yarn & Fabric
CSP and RKM Yarn Strength Calculator
Calculate CSP (count strength product) from lea strength and count, and RKM from single-end strength and tex. Both formulas, a worked example and why CSP and RKM do not convert exactly.
CSP
2,700
RKM
13.21km
Tex
19.68
The formula
CSP = lea strength (lbs) x Ne. RKM = single-end strength (cN) / Tex.
Worked example
Lea strength: 90 lbs, Yarn count: 30 Ne, Single-end strength: 260 cN. Result: CSP = 2,700; RKM = 13.21 km; Tex = 19.68.
CSP and RKM formulas
CSP (count strength product) = lea strength in pounds x yarn count in Ne. A 30 Ne yarn with a lea strength of 90 lbs has a CSP of 2,700.
RKM (resistance in kilometres) = single-end breaking force in cN / tex, where tex = 590.5 / Ne. A 30 Ne yarn is 19.68 tex; a single-end strength of 260 cN gives an RKM of 13.21 km, the length of yarn whose own weight would break it.
CSP comes from a skein (lea) test on a tester such as a lea strength tester; RKM comes from a single-yarn tester. They measure different things, so a mill quotes each from its own test.
Assumptions
- CSP and RKM are computed from their own measurements; converting one to the other needs the lea ratio, which is empirical and not assumed here.
Questions
- What is the formula for CSP?
- CSP = lea strength (lbs) x count (Ne). For example 90 lbs x 30 Ne = 2,700.
- What is the formula for RKM?
- RKM = single-end strength (cN) / tex. With tex = 590.5 / Ne, a 30 Ne yarn at 260 cN gives 260 / 19.68 = 13.21 km.
- Can I convert CSP to RKM?
- Not exactly. CSP and RKM come from different tests, and the ratio between them depends on the fibre, count and spinning system. Mills that need both measure both; a conversion factor is only an estimate fitted to one mill's own data.
- How do I convert TPI to TPM?
- Multiply TPI by 39.37. Use the TPI to TPM calculator for twist from the twist multiplier.
Read the guide
In the platform
Intelactory records which yarn lot went into which fabric roll, dye batch and carton as the work happens, so a count or GSM question traces back to its source.