Unit Converter
Convert between length, weight, volume, and temperature units instantly with visual comparison.
Length Converter
Conversion Result
1 cm = 0 in
Visual Comparison
Bar widths show the relative numeric magnitude of each value
All Length Conversions
1 cm equals:
Common Length Conversions
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How to Use the Unit Converter
Our free unit converter makes it simple to convert between different measurement units across four major categories: length, weight, volume, and temperature. Select a category using the tabs at the top, choose your "From" and "To" units from the dropdown menus, and enter a value in either input field. The conversion happens instantly as you type, with no need to press a button.
The converter supports two-way (bidirectional) conversion — you can edit either the left or right value and the other updates automatically. Use the swap button between the two inputs to quickly reverse your conversion direction. For length, weight, and volume conversions, a visual comparison bar shows the relative numeric magnitude of the two values, helping you build intuition about how different units relate to each other. For temperature, an interactive thermometer visualization shows where your temperature falls on a gradient scale with reference points for water's freezing point, human body temperature, and water's boiling point.
Below the main converter you will find an all conversions table that shows your entered value converted to every unit in the selected category at once. This is especially useful when you need to compare across multiple unit systems simultaneously. There is also a common conversions quick reference with clickable shortcuts for frequently used conversions like inches to centimeters, pounds to kilograms, and cups to milliliters.
Understanding Metric and Imperial Systems
The metric system, officially known as the International System of Units (SI), is used by virtually every country in the world for scientific and everyday measurements. It is built on base-10 relationships, making mental math and conversions within the system straightforward. For example, there are 1,000 millimeters in a meter, 1,000 grams in a kilogram, and 1,000 milliliters in a liter.
The imperial and US customary systems, still widely used in the United States for everyday purposes, have more irregular conversion factors. There are 12 inches in a foot, 3 feet in a yard, 5,280 feet in a mile, 16 ounces in a pound, and 8 fluid ounces in a cup. These relationships are harder to memorize, which is why a reliable unit converter is an essential tool for anyone who regularly works with both systems.
Tips for Common Conversions
A few handy mental shortcuts can help you estimate conversions quickly. One inch is roughly 2.5 centimeters, one mile is about 1.6 kilometers, and one kilogram is approximately 2.2 pounds. For temperature, double the Celsius value and add 30 for a rough Fahrenheit estimate that works well for everyday weather and cooking contexts. For precise calculations, use this converter to get results accurate to six significant digits.
For cooking and baking, accurate volume measurements are critical. Remember that US cups, tablespoons, and teaspoons differ from their metric equivalents. One US cup equals approximately 236.6 milliliters, not 250 mL as is sometimes assumed. One tablespoon is about 14.8 mL, and one teaspoon is approximately 4.9 mL. When precision matters — especially in baking — always use a converter to get exact measurements rather than relying on rough approximations.
Frequently Asked Questions
How do I convert metric units to imperial units?
Select your category (length, weight, or volume), choose the metric unit in the 'From' dropdown and the imperial unit in the 'To' dropdown, then type your value. The converter calculates the result instantly. For example, to convert kilometers to miles, select Length, set 'From' to Kilometer and 'To' to Mile, and enter your value. You can also click any common conversion shortcut below the converter to pre-fill a popular metric-to-imperial conversion.
What is the difference between fluid ounces and ounces?
Fluid ounces (fl oz) measure volume — the amount of space a liquid occupies — while ounces (oz) measure weight. One fluid ounce of water weighs approximately one ounce, but this only holds true for water at room temperature. For other liquids like honey or oil, the weight of one fluid ounce differs significantly. When cooking, pay close attention to whether a recipe calls for fluid ounces (volume) or ounces (weight) to get accurate measurements.
How do I convert Celsius to Fahrenheit?
The exact formula is F = (C × 9/5) + 32. For example, 25°C equals 77°F. For a quick mental estimate, double the Celsius value and add 30 — this gives a rough approximation that works well for everyday weather temperatures. Our converter uses the precise formula so you always get an accurate result, and the thermometer visualization shows where your temperature falls relative to common reference points like water freezing (0°C / 32°F) and boiling (100°C / 212°F).
Why does the United States use the imperial system?
The US inherited the imperial measurement system from Britain during the colonial era. Although Congress authorized the metric system for use in 1866 and most US government agencies and scientific institutions use metric, the imperial system remains dominant in everyday American life due to historical inertia, the cost of switching infrastructure, and cultural familiarity. The US is one of only three countries (along with Myanmar and Liberia) that have not officially adopted the metric system for general use.
What is the most common unit conversion?
The most frequently searched unit conversions include inches to centimeters, pounds to kilograms, Fahrenheit to Celsius, and miles to kilometers. In cooking, cups to milliliters and tablespoons to teaspoons are extremely common. The popularity of each conversion depends on context — travelers often need km/miles and Celsius/Fahrenheit, while cooks frequently convert between US cups and metric milliliters. Our common conversions section highlights the most useful conversions for each category.