CupRuler
Fresh loaves in a wicker basketPhoto: Mae Mu / Unsplash

Kitchen conversions

Millimeters to inches

Quick answer: One inch is exactly 25.4 millimetres, so inches = mm ÷ 25.4 and mm = inches × 25.4. Example: 100 mm = 3.94 inches, and 1/4 inch = 6.35 mm.

  • Ingredient weights: King Arthur Baking chart
  • Updated
  • Reviewed by Alex · How we calculate
Flour stored in a glass jar with a clip lid
King Arthur Baking chart1 cup all-purpose flour = 120 gSpooned and levelled
Photo: Ilinca Roman / Unsplash

1 inch = 25.4 mm exactly.

Where do these numbers come from?

Checked Oct 23, 2026. 1 inch is exactly 25.4 mm (NIST SP 811), so 100 mm ÷ 25.4 = 3.937 in.

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Chart

Frequently asked questions

How many mm in an inch?

Exactly 25.4 mm.