Drafting Ratio Calculator
Draw ratio from fiber diameter and target yarn count.
Inputs
Results
Total draft ratio
490
Per-zone draft490
Singles yards/lb19,600
Finished yarn yards/lb9,800
Roving per yard singles (g)0.02
Attenuation Factor490
TechniqueExtreme long draw — consider pre-drafting roving
How to Use This Calculator
- Enter the yards per pound of your roving or top (check the label or weigh a known length).
- Enter the target WPI (wraps per inch) of your desired finished yarn.
- Set the number of plies you plan to spin and ply together.
- Enter the number of drafting zones on your wheel or frame (1 for hand spinning).
- Read the total draft ratio — this tells you how far to attenuate the fiber from roving to singles.
- Use the singles yards per pound and finished yarn yards per pound outputs to plan your fiber purchase.
How the result changes with Target yarn WPI
| Target yarn WPI | Total draft ratio |
|---|---|
| 6.9 | 119.03 |
| 22 | 1,210 |
| 39 | 3,802.5 |
| 54 | 7,290 |
What each input means
- Roving yards/lb
- Yards per pound of your input roving/top (typical handspinning roving: 30-60).
- Target yarn WPI
- Wraps per inch of your target finished yarn.
- Number of plies
- Number of singles to be plied together.
- Draft zones
- Number of drafting zones (1 for hand spinning, 2-4 for industrial frames).
What each result means
- Total draft ratio
- How many times the fiber must be drawn out (attenuated) from roving to singles.
- Per-zone draft
- Draft ratio for each individual drafting zone.
- Singles yards/lb
- Required yards per pound for each single.
- Finished yarn yards/lb
- Yards per pound of the finished plied yarn (McMorran's balance).
- Roving per yard singles (g)
- Grams of roving consumed per yard of singles.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersRoving yards/lb = 40, Target yarn WPI = 14, Number of plies = 2, Draft zones = 1 = 4 input(s) provided
- Calculate Total draft ratioTotal draft ratio = singlesYardsPerLb / rovingYardsPerLb490 = 490
- Calculate Per-zone draftPer-zone draft = pow(totalDraftRatio, 1 / draftZones)490 = 490
- Calculate Singles yards/lbSingles yards/lb = yarnYardsPerLb * plies19600 = 19600
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
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