Label Roll Diameter & Length Calculator

How to use it: enter your roll's core diameter, its full (new) outer diameter, material thickness, and label length/gap. To check how many labels are left on a partly used roll, lower "current roll diameter" to what you measure on the actual roll.

Formula. A wound roll's cross-sectional area (the ring between the core and the outer diameter) equals the material thickness times the total length wound onto it - the same approximation used industry-wide for label, paper and film rolls:

Length = π × (outer radius² − core radius²) / thickness

Label count is that length divided by the label's repeat pitch - its length along the web plus the gap to the next label: Count = length ÷ (label length + gap). The required diameter for a target count runs the same formula in reverse.

Worked example. With the defaults (76 mm core, 200 mm full OD, 0.15 mm thickness, 100 mm label + 3 mm gap = 103 mm pitch): full length = π × (100² − 38²) / 0.15 ≈ 179.2 m, giving ≈1,739 labels. At a worn-down 150 mm current diameter: remaining length = π × (75² − 38²) / 0.15 ≈ 87.6 m, or ≈850 labels left.

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Core outer diameter

76 mm

Full (new) roll diameter

200 mm

Current roll diameter

150 mm

Material thickness (caliper)

0.15 mm

Label length along the web

100 mm

Gap between labels

3 mm

Target label count

500

Primary result: Full roll length: 179.2 m.

• Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
• Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
• When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.

This is a geometric estimate, not a measurement of your actual roll. Real rolls rarely wind as perfect concentric layers - winding tension, liner stretch, and compression from roll weight all make the true length vary somewhat from this ideal calculation, especially on larger rolls. Treat the result as a close planning estimate.

It assumes constant material thickness and a constant label pitch along the whole roll. It does not account for splices, a leader/trailer section with no labels, or a partially peeled first label.