Convert lengths quickly between dozens of units — metric, imperial, maritime, astronomical and historical — with an easy searchable selector.
Length Converter
Enter the numeric length value you want to convert.What is the Length Converter?
The Length Converter is an online tool that converts numeric length values between different units of measurement. It supports common metric and imperial units (meters, kilometers, inches, feet, miles), maritime units (nautical miles, fathoms), astronomical measures (light years, astronomical units, parsecs) and historical/rare units (cubits, hands, barleycorns).
Why you need a Length Converter
Working with measurements often requires switching units depending on context — engineering blueprints use metres, carpenters prefer inches, sailors use nautical miles, and astronomers use light years or parsecs. This converter saves time, reduces errors, and standardizes values when sharing or publishing results.
Quick facts
– Converts across 30+ units from the atomic scale (nanometers) to astronomical scales (light years & parsecs).
– Grouped unit lists for easier browsing (Metric, Imperial, Maritime, Astronomical, Historical).
– Searchable dropdowns — type to filter units quickly.
– Copy results to clipboard and swap units with one click.
Real life examples
– A builder converting 2.5 meters into inches to check a hardware spec.
– A sailor converting 15 nautical miles into kilometers for a voyage plan.
– A student converting astronomical distances from astronomical units (AU) to kilometers for an assignment.
– A historical researcher converting cubits to meters to estimate an ancient structure’s dimensions.
How to use the converter
1. Enter the numeric value you want to convert in the input field.
2. Choose the From unit (type in the search box to filter).
3. Choose the To unit (type in the search box to filter).
4. Result updates automatically. Use the ⇄ button to swap units or the “Copy Result” button to copy the text to your clipboard.
Why this conversion is accurate
The converter uses a single canonical base (meters). Every unit has a fixed factor defined as the amount of that unit contained in one meter (for example, 1 meter = 100 centimeters, so cm.factor = 100). Conversions are performed via meters to avoid rounding inconsistencies across direct pair conversions.
Conversion formulas
If factor_A is the factor value for unit A and factor_B is the factor for unit B (both defined as “units per meter”), then:
meters = value_in_A / factor_A
value_in_B = meters * factor_B
— combined formula —
value_in_B = value_in_A * (factor_B / factor_A)
Example: converting 2500 mm (millimetres) to meters: factor_mm = 1000 (because 1 m = 1000 mm) meters = 2500 / 1000 = 2.5 m
Example: converting 1 nautical mile to kilometers: factor_nmi = 0.0005399568 factor_km = 0.001 km = 1 * (0.001 / 0.0005399568) ≈ 1.852 km
All formulas (summary)
– Convert A → B: value_B = value_A × (factor_B / factor_A)
– Convert to meters: meters = value_A ÷ factor_A
– Convert from meters: value_B = meters × factor_B
Tips
– Use the search box above each dropdown to quickly find units (e.g., type “mile” to find Miles and Nautical Miles).
– For very large or very small results the converter shows scientific exponential notation for readability.
– If you need repeated conversions with the same units, use the swap button then change the input value to convert in the opposite direction quickly.
Frequently Asked Questions (FAQ)
What units does the converter support?
It supports metric (m, cm, mm, µm, nm, Å, km), imperial (in, ft, yd, mi, chains, furlongs), maritime (nmi, fathoms, cable), astronomical (AU, ly, pc), surveying (rods, links) and historical units (cubit, span, hand, barleycorn).
Is the converter accurate enough for engineering work?
Yes — the converter uses standard exact factors for unit definitions and converts via a single-meter base. For critical engineering work, always confirm the unit standards required (e.g., use survey feet vs international feet if specified) and the number of decimal places you need.
Why does the result sometimes show scientific notation?
When values are extremely large or extremely small, scientific notation (exponential) keeps the result readable and avoids misleading long strings of digits.
Can I copy the result?
Yes — click the “Copy Result” button to copy the displayed conversion text to your clipboard.
Are historical units exact?
Historical units (like cubits, palms, barleycorns) vary historically and regionally. The converter uses commonly accepted average equivalents for educational purposes; they are approximate.
What if I need a unit not listed?
Contact us with the unit name and definition (how many of that unit equal one meter) and we can consider adding it.
Disclaimer
The Length Converter is provided for educational and convenience purposes. While care has been taken to include standard conversion factors, some historical units are approximate. For professional, legal, or safety-critical calculations always verify unit definitions and rounding with authoritative standards or consult a qualified professional.