Metric vs Imperial: A Simple Conversion Cheat Sheet

Metric and imperial units describe the same quantities with different scales. Reliable conversion depends on using the correct factor and preserving enough precision.

Start with the idea

SI metric units are built around powers of ten. Common U.S. customary and imperial units use fixed factors such as 1 inch = 2.54 centimetres exactly.

Convert by multiplying the source value by the source-to-target factor. For calculations involving area or volume, the conversion factor must be squared or cubed.

Worked example

Convert 6 feet to metres. Six feet equals 72 inches. Multiply 72 by 2.54 to get 182.88 cm, or 1.8288 m.

For area, 1 square foot is not 0.3048 square metres. The factor must be squared: 0.3048² = 0.09290304 m².

Quick reference

Common mistakes

• Mixing mass and weight terminology
• Using a length factor directly for area or volume
• Rounding too early
• Combining units without converting first

Practical steps

1. Write the source value and unit.
2. Choose the exact or accepted conversion factor.
3. Apply squared or cubed factors when needed.
4. Keep extra digits during calculation.
5. Round only the final result.

Sources and review note

• NIST SI length guidance
• NIST SI mass guidance

This article was reviewed for language, calculation examples and source links by Yasser Chahir, Fynzo editor. Last reviewed: July 31, 2026. It is general educational information, not medical, financial, tax or legal advice.