Centimeters to Inches Conversion Chart

The Formula

Inches = Centimeters ÷ 2.54

Centimeters = Inches × 2.54

Or equivalently: Inches = Centimeters × 0.3937

1 inch is defined as exactly 2.54 centimeters by international agreement (1959). The conversion is exact, not approximate.

Quick Mental Conversions

• 10 cm ≈ 4 inches (precise: 3.94″)
• 25 cm ≈ 10 inches (precise: 9.84″)
• 50 cm ≈ 20 inches (precise: 19.69″)
• 100 cm = 1 meter ≈ 39.37 inches (just over 3 feet 3 inches)
• 1 meter ≈ 3.28 feet
• 1 foot = 30.48 cm
• 1 yard = 91.44 cm

When Precision Matters

For everyday tasks (cooking, height), rounding to the nearest centimeter or quarter inch is fine. For sewing and crafting, work to the nearest 1/8 inch (3 mm). For woodworking, 1/16 inch (1.5 mm) is the standard. For machining and precision engineering, work in thousandths of an inch (0.001″ = 0.0254 mm) or hundredths of a millimeter.

Reading a Metric Ruler

A standard metric ruler shows centimeters as large markings (usually labeled 1 through 30) and millimeters as small subdivisions (10 mm per cm). Some rulers also include a half-cm marking. Always read from the zero mark, not the end of the ruler, which is usually a few millimeters past the start of the scale.

Reading an Imperial Ruler

A US ruler typically shows inches subdivided into halves, quarters, eighths, and sixteenths. The longer the tick mark, the “rounder” the fraction. From longest to shortest: 1/2 inch > 1/4 inch > 1/8 inch > 1/16 inch. Each shorter tick splits the space between the longer ticks in half.

The History of the Inch

The inch has been defined many ways over centuries. Early British definitions used the length of three barleycorns laid end-to-end. The 14th-century English statute defined the inch as 1/36 of a yard. By the 18th century, the inch had been redefined by reference to the brass standard yard kept in London. The current definition (1 inch = 2.54 cm exactly) came from the 1959 International Yard and Pound Agreement signed by the US, UK, Canada, Australia, New Zealand, and South Africa, which unified the inch across the English-speaking world by tying it to the metric system.

The History of the Centimeter

The centimeter is 1/100 of a meter. The meter was originally defined in 1793 as 1/10,000,000 of the distance from the equator to the North Pole. After several artifact-based definitions in the 19th and 20th centuries, the modern definition (since 1983) ties the meter to the speed of light: 1 meter = the distance light travels in 1/299,792,458 of a second in a vacuum. The centimeter is exactly 1 cm = 0.01 m by definition.