Inch Converter — Free Online Length Unit Converter

How to Use the Inch Converter

1. Enter your measurement value: Type the numeric value you want to convert into the Value field. The converter accepts whole numbers, decimals, and very large or small values. For example, enter 12 to convert 12 inches, or 2.5 to convert two and a half of any selected unit.
2. Select the source unit: Use the From Unit dropdown to choose the unit you are converting from. The default is set to inches, but you can select from feet, centimeters, millimeters, meters, yards, kilometers, or miles. The converter works bidirectionally, so you can convert from any unit to all others.
3. View all conversions instantly: As soon as you enter a value or change the unit, the results panel updates in real time. Every supported length unit is displayed simultaneously, eliminating the need to perform multiple separate conversions. This is especially useful when you need to compare measurements across different systems.
4. Use the summary for quick reference: The summary box at the bottom of the results panel provides a concise one-line statement showing the most commonly needed conversions in inches, centimeters, and feet for easy copying and reference.

All results update in real time as you change any value. Try different units to explore how measurements relate across the imperial and metric systems.

Inch Conversion Formulas

Variables Explained

• Inches (in): The base unit in the imperial length system. One inch is defined as exactly 25.4 millimeters by international agreement since 1959. Inches are divided into fractions (1/2, 1/4, 1/8, 1/16) in everyday use and into thousandths (mils) in engineering applications.
• Centimeters (cm): One hundredth of a meter in the metric system. One centimeter equals approximately 0.3937 inches. Centimeters are the most common metric unit for body measurements, clothing sizes, and everyday object dimensions in countries using the metric system.
• Feet (ft): An imperial unit equal to exactly 12 inches or 0.3048 meters. Feet are widely used in the United States and United Kingdom for measuring height, room dimensions, and elevation. Altitude in aviation is universally reported in feet.
• Meters (m): The base unit of length in the International System of Units (SI). One meter equals approximately 39.37 inches or 3.281 feet. The meter is defined by the speed of light and is the global standard for scientific and engineering measurements.
• Millimeters (mm): One thousandth of a meter, providing high precision for small measurements. One millimeter equals approximately 0.03937 inches. Millimeters are standard in mechanical engineering, machining, and medical measurements.

Step-by-Step Example

Suppose you need to convert a 65-inch television screen measurement to metric units:

1. Start with the value: 65 inches
2. Convert to centimeters: 65 x 2.54 = 165.1 cm
3. Convert to meters: 65 x 0.0254 = 1.651 m
4. Convert to millimeters: 65 x 25.4 = 1,651 mm
5. Convert to feet: 65 / 12 = 5.417 ft (5 feet 5 inches)

So a 65-inch TV has a diagonal measurement of approximately 165 centimeters or 1.65 meters. This is the diagonal screen size, not the overall TV width, which is typically a few inches larger due to the bezel.

Practical Examples

Example 1: Amanda Measures Furniture for an International Move

Amanda is relocating from New York to Berlin and needs to determine whether her American-sized furniture will fit in her new apartment, where dimensions are listed in centimeters. Her sofa is 84 inches long and 36 inches deep, and the apartment living room is listed as 350 cm x 400 cm. Using the inch converter:

• Sofa length: 84 inches x 2.54 = 213.4 cm
• Sofa depth: 36 inches x 2.54 = 91.4 cm
• Room dimensions: 350 cm x 400 cm
• Clearance along the wall: 350 - 91.4 = 258.6 cm remaining

Amanda confirms her sofa will fit along the 400 cm wall with over 186 cm to spare, and the 91.4 cm depth leaves plenty of walking space. She repeats this process for her bookshelf (72 inches = 182.9 cm tall) and dining table (60 inches = 152.4 cm long) to plan the entire layout.

Example 2: David Orders Custom Window Blinds

David measures his windows in inches for custom blinds, but the manufacturer's website requires millimeters for precision ordering. His three windows measure 48 inches wide, 36 inches wide, and 24 inches wide, all 60 inches tall. Using the inch converter:

• Window 1 width: 48 inches x 25.4 = 1,219.2 mm
• Window 2 width: 36 inches x 25.4 = 914.4 mm
• Window 3 width: 24 inches x 25.4 = 609.6 mm
• All heights: 60 inches x 25.4 = 1,524 mm

David enters these millimeter values on the manufacturer's website and orders blinds with precise measurements, avoiding the common mistake of converting imprecisely and ending up with blinds that are too short or narrow.

Example 3: Maria Compares Height for a Visa Application

Maria needs to report her height in centimeters on an international visa application. She knows she is 5 feet 4 inches tall but needs to convert this to a single centimeter value. Using the inch converter:

• Total height in inches: 5 x 12 + 4 = 64 inches
• Height in centimeters: 64 x 2.54 = 162.56 cm
• Rounded for the form: 163 cm
• Height in meters: 1.63 m

Maria enters 163 cm on her application. This conversion is one of the most commonly needed by Americans traveling abroad, as most countries record height in centimeters on official documents, passports, and medical records.

Example 4: Kevin Converts a Recipe's Pan Size

Kevin found a European baking recipe that calls for a 26 cm round cake pan, but his pans are labeled in inches. He needs to find the closest match from his collection of 8-inch, 9-inch, and 10-inch pans:

• 26 cm to inches: 26 / 2.54 = 10.24 inches
• His 10-inch pan = 25.4 cm (close to 26 cm)
• Difference: 26 - 25.4 = 0.6 cm (negligible)

Kevin uses his 10-inch pan, which is only 0.6 cm smaller than the recipe specifies. This tiny difference will not affect the baking result. He also converts the 20 cm pan called for in another recipe and finds his 8-inch pan (20.32 cm) is a near-perfect match.

Inch Conversion Reference Table

Conversion factors: 1 inch = 2.54 cm = 25.4 mm = 0.0254 m = 1/12 foot.

Tips and Complete Guide

Understanding the Inch in Historical Context

The inch has a long history dating back to at least the 7th century. Originally based on the width of a man's thumb, it was later standardized through various royal decrees. In 1959, the international inch was defined as exactly 25.4 millimeters by agreement among six English-speaking nations: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. This standardization eliminated small discrepancies between the US survey inch and the British imperial inch, ensuring that one inch means the same thing everywhere in the world. The US survey inch remained in limited use for land surveying until 2023, when the National Geodetic Survey officially retired it.

When to Use Inches vs. Metric Units

In the United States, inches remain the standard for most consumer products, construction materials, and everyday measurements. Screen sizes for TVs, monitors, tablets, and phones are measured in inches worldwide, even in metric countries. Construction lumber, plumbing fittings, and hardware in the US use inch-based dimensions. However, international trade, scientific research, medical dosing, and manufacturing increasingly require metric units. Knowing how to convert quickly between inches and centimeters or millimeters is essential for anyone working across these systems. When precision matters, such as in machining or laboratory work, always verify your conversion to the appropriate number of decimal places.

Fractional Inches and Decimal Conversion

In construction and woodworking, inches are often expressed as fractions rather than decimals. The most common fractions are halves (1/2), quarters (1/4), eighths (1/8), and sixteenths (1/16). To convert a fractional inch to a decimal, divide the numerator by the denominator: 3/8 inch equals 0.375 inches. Some precision work uses thirty-seconds (1/32) or sixty-fourths (1/64). A key practical tip is that 1/16 of an inch equals 1.5875 mm, which is close to 1.6 mm. When converting fractional inches to metric for ordering parts, round to the nearest 0.5 mm for standard tolerances or use the exact value for precision applications. Our converter handles both whole numbers and decimals, so enter 0.375 for 3/8 inch.

Common Mistakes to Avoid

• Confusing inches with centimeters on imported products: Many products sold internationally list dimensions in centimeters. Always check whether the listed measurement is in inches or centimeters before purchasing, especially for clothing, electronics, and furniture. A 32 cm waist is very different from a 32-inch waist.
• Forgetting that nominal lumber sizes differ from actual sizes: A 2x4 board does not actually measure 2 inches by 4 inches. The actual dimensions are 1.5 inches by 3.5 inches after milling and drying. Always use actual dimensions, not nominal ones, when converting for precise applications.
• Rounding too aggressively: When converting inches to centimeters for precision work, rounding 2.54 down to 2.5 introduces a 1.6% error. Over a 100-inch measurement, that error grows to 4 centimeters, which can cause significant fitting problems in construction or manufacturing.
• Using the wrong conversion direction: Multiplying by 2.54 converts inches to centimeters, while dividing by 2.54 converts centimeters to inches. Using the wrong operation gives a result that is off by a factor of 6.45, which is immediately noticeable for large values but can slip past unnoticed for small ones.
• Ignoring the difference between inches and square inches: Length conversion (inches to cm) uses the factor 2.54, but area conversion (square inches to square centimeters) uses 6.4516 (which is 2.54 squared). For volume, the factor is cubed. Always ensure you are using the correct conversion for the dimension type.

Frequently Asked Questions