Skip to main content
zcohen-nerd

Pitch: The Number That Saves You

Pitch is the center-to-center spacing between adjacent contacts. It is the single most discriminating, easiest-to-measure number on any connector — and measuring it correctly resolves most "which family is this?" questions before they start.

Why pitch matters​

  • Common hobby pitches include 2.54 mm (0.1 in), 2.5 mm, 2.0 mm, 1.5 mm, 1.25 mm, and 1.0 mm — and several families exist at each of them.
  • Pitch alone does not identify a connector — it narrows the field so latch, housing, and drawing comparison can finish the job.
  • Photos are unreliable for pitch. A 2.0 mm and a 2.5 mm housing look identical on a phone screen; the parts will not mate.
  • Inch/mm confusion matters: 2.54 mm is 0.1 inch; 2.5 mm is not. They differ by only 0.04 mm per position — invisible on 2 pins, binding and contact misalignment across 10.
  • 2.5 mm and 2.54 mm are not always interchangeable, and clone listings often round one to the other. Assume nothing; measure and check the drawing.

How to measure it right​

Measuring one gap between two small contacts multiplies your caliper error. Spread the error across the row instead:

For N contacts, measure from the center of the first contact to the center of the last contact, then divide by N−1.

Example: for a 4-position connector, measure center-to-center from contact 1 to contact 4 and divide by 3. A first-to-last reading of 7.5 mm ÷ 3 = 2.5 mm pitch; 7.62 ÷ 3 = 2.54 mm. The full-row measurement is what separates those two cleanly.

Diagram: a four-position connector with a discouraged single-gap measurement above and the preferred full-row center-to-center measurement below, divided by N minus one

One gap hides caliper error inside a small number; the full row spreads it thin.

Practical tips:

  • Measure the contacts or cavities, not the housing edges.
  • On a header, measuring pin 1 outside-edge to pin N outside-edge also works: that equals the center-to-center distance because the pin widths cancel (half a pin on each end).
  • If you can't get calipers on the mating face, measure the solder tails on the board side.
  • Cross-check the total row length against the candidate family's drawing — drawings dimension exactly this.

Related: How to Identify an Unknown Connector · JST Is Not One Connector — where a 0.5 mm pitch difference is the whole story.