TOOLS
Estimate the diameter of a wire bundle or cable bundle from wire quantities and outside diameters. See a validated cross-section, add copper braid or PET sleeving, and check whether the bundle fits a circular opening — in mm or inches.
Results update as you type. Click a diameter to copy it, or the corner icon for the full summary. Tip: type "22 AWG" as an OD for a bare-conductor estimate, or pick a covering preset.
Before shielding & sleeving
Including shielding & sleeving
Estimated ·
This calculator provides engineering guidance only. Actual bundle dimensions depend on wire construction and assembly, so verify critical fits with a physical sample.
quick guide
Enter the number of wires and the outside diameter of each, and the calculator gives you the diameter of the whole bundle.
1. Add a row for each wire or cable type: quantity × outside diameter in mm or inches. Use Add wire group for each different size. Type “22 AWG” as the diameter for a quick bare-conductor estimate.
2. Add shielding and sleeving, if needed. Enter each layer’s thickness per side. Choose a Copper braid or PET sleeving preset for an initial estimate, or enter your own values.
3. Read the results as they update. Bare bundle shows the diameter before overall coverings. Overall diameter appears when you add shielding or sleeving. The drawing shows the cross-section and packing density.
4. Switch to Check opening fit to compare the bundle with an existing opening. Enter its clear inside diameter: the usable bore of a grommet or backshell cable entry.
Use the finished outside diameter, including the wire insulation or cable jacket. Two wires sold as the same AWG can have noticeably different outside diameters depending on their insulation, so take the value from the wire’s datasheet. For a group of complete cables, enter each cable’s jacket diameter and quantity.
Typing “22 AWG” into an OD field gives a bare solid-conductor estimate. Replace it with the finished OD before checking fit. In the results, Bare bundle means before the bundle’s overall shielding and sleeving. The insulation already included in your wire inputs still counts.
Suppose a harness branch contains seven wires, each with a finished OD of 2 mm. Enter a quantity of 7 and an OD of 2 mm, with shielding and sleeving set to None. The wires fit six around one, making the bundle three wire diameters across:
Bare bundle diameter: 3 × 2 mm = 6 mm
Now suppose the design adds 0.2 mm of shielding and 0.3 mm of sleeving, each measured per side. Enter these as custom values. Each layer adds thickness on both sides of the bundle:
Overall diameter: 6 + (2 × 0.2) + (2 × 0.3) = 7 mm. That is the figure to compare with a backshell cable entry or a grommet bore.
Switch to Check opening fit and enter 8 mm. The calculator reports Fit confirmed for this arrangement. The opening is 1 mm wider than the covered bundle, leaving 0.5 mm around it when centred. These covering thicknesses and the opening size are example inputs, not recommended allowances for every harness.
Wires in a bundle are circles packed inside a larger circle, so the diameter is a circle-packing problem, not an area sum. The calculator uses the quantity and finished outside diameter of each wire to build an arrangement, then checks it for overlaps and boundary crossings. It adds twice the shielding thickness and twice the sleeving thickness to obtain the overall diameter.
Simply adding wire areas misses the gaps between round wires. In the seven-wire example, the wires occupy 77.8% of the bare bundle’s circular area. That is the packing density. It excludes the overall shielding and sleeving. Different counts and sizes give different densities.
For larger or mixed bundles, Improve results gives the calculator more time to look for a tighter arrangement. A longer search may reduce the estimate, but it does not guarantee the smallest possible diameter.
Fit not confirmed means the current arrangement exceeds the available opening, but a tighter arrangement may still fit. Try more time with Improve results, or consider a larger opening. Cannot fit under these assumptions means the calculator has established that the opening is too small under its geometric model.
The result is a geometric estimate for round wires under ideal conditions. A manufactured wire or cable bundle also carries lay, twist, tape and tolerances, which can increase its measured diameter. For critical dimensions, measure a sample.
Click a result diameter to copy it, or use Export PDF or Export PNG to save the calculation and cross-section for your documentation.
Need to convert a conductor size? Use the AWG to mm Calculator. Routing the finished bundle? Check its minimum bend radius with the Cable Bend Radius Calculator, or browse all our engineering tools.
