Wire Wrapping Length Calculator
Wire wrapped around a mandrel or bead follows a circle drawn by its own centreline, and that circle's diameter is the mandrel plus the wire. Five wraps of 0.8 mm wire on an 8 mm mandrel take 138 mm. The wrapped section stands wraps × wire diameter tall, here 4 mm, which is the figure to check when sizing a bail.
Your numbers
Wire length
138.2mm
Finished length
4mm
Formula
Wire length = Wraps × π × (Mandrel diameter + Wire diameter)
Cut 2–3 cm extra at each end. Without a tail to grip with pliers you cannot tighten the last wrap, and the wire stretches slightly as you pull it in. Heavy wire, 0.8 mm / 20 gauge and up, resists wrapping by hand, so real coils come out looser than the arithmetic.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Mandrel diameter (mm)The mandrel across; it becomes the ring's inside diameter. | 8 | 0.5 and up |
| Wire diameter (mm)Wire thickness; it adds to the ring diameter twice. | 0.8 | 0.1 and up |
| WrapsHow many turns; each eats one circumference. | 5 | 1 and up |
Step by step
Quick reference table
Results when only Mandrel diameter (mm) changes and everything else stays put.
| Mandrel diameter (mm) | Wire length (mm) | Finished length (mm) |
|---|---|---|
| 4 | 75.4 | 4 |
| 6 | 106.8 | 4 |
| 8 | 138.2 | 4 |
| 12 | 201.1 | 4 |
| 16 | 263.9 | 4 |
What each result means
| Result | At default values |
|---|---|
| Wire length (mm)Wire needed, before what you trim and waste. | 138.2 |
| Finished length (mm)The length when finished. | 4 |
Common mistakes
Cut 2–3 cm extra at each end. Without a tail to grip with pliers you cannot tighten the last wrap, and the wire stretches slightly as you pull it in. Heavy wire, 0.8 mm / 20 gauge and up, resists wrapping by hand, so real coils come out looser than the arithmetic.
Glossary
- Mandrel diameter
- The mandrel across; it becomes the ring's inside diameter.
- Wire diameter
- Wire thickness; it adds to the ring diameter twice.
- Wraps
- How many turns; each eats one circumference.
- Wire length
- Wire needed, before what you trim and waste.
- Finished length
- The length when finished.
Frequently asked questions
Q. How is Wire Wrapping Length Calculator calculated?
Wire length = Wraps × π × (Mandrel diameter + Wire diameter) — Wire wrapped around a mandrel or bead follows a circle drawn by its own centreline, and that circle's diameter is the mandrel plus the wire. Five wraps of 0.8 mm wire on an 8 mm mandrel take 138 mm. The wrapped section stands wraps × wire diameter tall, here 4 mm, which is the figure to check when sizing a bail.
Q. Can you walk through an example?
With Mandrel diameter 8mm, Wire diameter 0.8mm, Wraps 5, the answer is Wire length 138.2mm.
Q. What do I need to enter?
Enter Mandrel diameter, Wire diameter, Wraps. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Mandrel diameter (mm) moves the answer to Mandrel diameter (mm) 4 → Wire length (mm) 75.4 and Mandrel diameter (mm) 16 → Wire length (mm) 263.9. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Cut 2–3 cm extra at each end. Without a tail to grip with pliers you cannot tighten the last wrap, and the wire stretches slightly as you pull it in. Heavy wire, 0.8 mm / 20 gauge and up, resists wrapping by hand, so real coils come out looser than the arithmetic.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.