Inches to CM Converter
Length Converter
Precision conversion between Imperial (US) and Metric units.
Report Bug While the United States relies on the Imperial system (Inches, Feet, Yards), the rest of the world and the entire scientific community operate on Metric (Centimeters, Meters). The Inches to CM Converter eliminates the guesswork. It uses the precise international conversion factor to transform US standard lengths into metric measurements, ensuring your furniture fits, your 3D print succeeds, and your international shipping dimensions are accurate.
Whether you are converting your height from "5 foot 10" or measuring a drill bit size, precision is non-negotiable.
📐 The International Standard (Since 1959)
There is no "rounding" here. Since the International Yard and Pound Agreement of 1959, the inch has been legally defined as exactly 25.4 millimeters.
Quick Rules of Thumb:
- 1 Inch: Exactly 2.54 cm.
- 1 Foot (12 Inches): 30.48 cm.
- 1 Meter: Approximately 39.37 inches.
📏 Specification Sheet: Common Conversions
From ruler fractions to common TV sizes, here is how US measurements translate to the Metric system with high precision.
| US IMPERIAL (Inches) | FRACTIONAL | METRIC (Centimeters) |
|---|---|---|
| 0.5 inch | 1/2" | 1.27 cm |
| 1.0 inch | 1" (Standard) | 2.54 cm |
| 6.0 inches | 1/2 Foot | 15.24 cm |
| 12.0 inches | 1 Foot | 30.48 cm |
| 55.0 inches | Large TV | 139.70 cm |
| 70.0 inches | 5' 10" Height | 177.80 cm |
Engineer's Tip: When doing construction or 3D printing, never round 2.54 to 2.5. Over a length of 100 inches, that small "rounding error" results in a gap of 4 centimeters (1.5 inches), which is enough to ruin a project.
US Context: Why the Confusion?
- Ruler Fractions: US rulers are divided into fractions (1/16, 1/8, 1/4) rather than decimals. This makes conversion tricky. (e.g., 3/8 inch = 0.375 inch = 0.9525 cm).
- Paper Sizes: The US uses "Letter" (8.5 x 11 inches), while the world uses A4 (21 x 29.7 cm). They are close, but not identical, causing printing issues.
- Screen Sizes: Globally, screen sizes (TVs, Monitors, Smartphones) are marketed in Inches diagonally, even in metric-dominant countries like Germany or Japan.
Frequently Asked Questions (FAQs)
How do I convert my height (Feet and Inches) to CM?
First, convert the feet to inches.
Example: 5' 10".
1. Multiply feet by 12: 5 × 12 = 60 inches.
2. Add the extra inches: 60 + 10 = 70 inches.
3. Multiply by 2.54: 70 × 2.54 = 177.8 cm.
Is 1 inch exactly 2.54 cm?
Yes. It is not an approximation. The definition was standardized in 1959 by the US, UK, Canada, Australia, and South Africa to be exactly 25.4 millimeters (2.54 cm).
What is a "Mil" in US manufacturing?
Do not confuse "Mil" with Millimeter. In US machining, a "Mil" is 1/1000th of an inch (0.001 inch). This is equal to 0.0254 mm.
How to do mental math for inches to cm?
For a rough estimate, multiply the inches by 2.5.
Example: 10 inches × 2.5 = 25 cm. (The real answer is 25.4 cm, so you are very close for non-precision tasks).
Why does the US still use Imperial?
It's mostly due to industrial inertia and infrastructure cost. Retooling every factory, changing every road sign, and rewriting every building code from Imperial to Metric would cost billions of dollars.
