Identify a Nail Size

A free tool for identifying a nail. Lay the nail on a calibrated on-screen ruler, or print a 1:1 paper gauge, and read its US penny size (d), length in millimetres and inches, and shank thickness — no caliper or tape measure needed.

How to identify a nail

Pick a mode

Choose "Measure on screen" for a calibrated ruler, or "Print a gauge" to download a paper sheet.

Calibrate or print at 100%

On screen, match the blue rectangle to a bank card. On paper, print at Actual size and check the 50 mm bar.

Measure and read

Lay the whole nail along the length ruler and the shaft across the thickness ruler; the tool shows the penny size.

Read a nail's penny size, length and shank thickness

Features

Two ways to measure Penny size + metric 50 mm verification bar One-time calibration

Frequently Asked Questions

What is a nail's "penny size"?

Penny size, written with a "d" (for example 8d), is the traditional US way of sizing nails. It is set by the nail's length — an 8d nail is 2.5 inches long. This tool measures the length and reports the matching penny size.

How do I measure a nail accurately?

Lay the whole nail along the length scale, from the tip to the underside of the head. For the shank, lay the shaft across the thickness scale. This tool does both on a calibrated screen or a printed gauge.

What is the shank diameter for?

The shank diameter is the thickness of the nail's wire. It matters when matching a replacement nail or choosing a pilot-hole drill bit. The tool reports the typical shank for the identified size and your measured value.

Can I use this without a printer?

Yes. The "Measure on screen" mode needs only a calibrated display and any card for reference. The printable PDF is optional.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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Who is this tool for?

🔌 Electronics Enthusiasts

Published 18 May 2026