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length-converter

A length converter translates a distance or dimension between metric units (millimeters, centimeters, meters, kilometers) and imperial/US units (inches, feet, yards, miles), plus specialist units like nautical miles and astronomical units, using exact SI-defined conversion factors. The ZTools Length Converter handles 15+ length units, updates live as you type, supports decimal and fractional inputs (e.g., "5'10"" auto-parses to 70 inches), and shows side-by-side conversions to all common units so users see "5 ft = 1.524 m = 60 in = 152.4 cm" in one screen.

Use cases​

Shopping for clothes or furniture from international stores​

A European chair lists "75 cm tall"; you think in inches. Convert to 29.5 in. Quick reality-check before ordering.

Travel — running, hiking, driving distances​

"The trail is 8 km" — that's 5 miles. "Speed limit 100 km/h" = 62 mph. Quick mental sanity-checks while abroad.

Construction and DIY​

Plans in metric; lumber in feet. Convert to plan dimensions you can actually buy. Avoid measuring twice and cutting wrong.

Engineering specs​

A part datasheet uses millimeters; your assembly drawing is in inches. Convert without dropping a decimal place — those errors propagate downstream.

How it works​

  1. Enter a length — Decimal numbers accepted. Special inputs like "5'10"" (5 feet 10 inches) parse correctly.
  2. Pick the source unit — Mm, cm, m, km, in, ft, yd, mi, nautical mile, AU.
  3. See conversions to all common units — Single screen shows the source in all other length units. Saves re-clicking to convert one at a time.
  4. Copy any value with one click — Click any unit row to copy that converted value. Useful for spreadsheet entry.

Examples​

Input: 5 km

Output: 5000 m | 16,404 ft | 3.107 mi | 5,468 yd

Input: 6 ft

Output: 1.829 m | 182.88 cm | 1828.8 mm | 72 in

Input: 1 mile

Output: 1.609 km | 1609.344 m | 5280 ft | 1760 yd

Frequently asked questions​

How exact are the conversions?

Modern SI definitions make most conversions exact. 1 inch = 25.4 mm exactly. 1 mile = 1609.344 m exactly. The converter uses these exact factors with full floating-point precision.

What's a nautical mile and when is it used?

1 nautical mile = 1852 m exactly. Defined as ~1 minute of latitude. Used in marine navigation, aviation, and meteorology where the spherical Earth makes statute miles awkward.

Why does the UK use both km and miles?

Officially metric, but cars drive in mph and road signs are in miles for historical reasons. Cycling and running often use km; driving uses miles. UK is an unusual mix.

How do I convert "5'10"" to centimeters?

5 feet = 152.4 cm, 10 inches = 25.4 cm, total = 177.8 cm. The converter parses "5'10"" automatically; you don't need to compute manually.

What about the astronomical unit (AU)?

1 AU ≈ 149.6 million km — the Earth-Sun distance. Used in space science where km would produce inconveniently large numbers.

Tips​

  • For quick mental conversion: 1 m ≈ 3.28 ft, 1 km ≈ 0.62 mi, 1 in = 2.54 cm.
  • Always work in one unit system from start to finish — converting in the middle of a calculation is error-prone.
  • For very large distances (astronomy), prefer light-years or parsecs; very small (microscopy) use micrometers or nanometers.
  • Imperial measurements often have multiple decimal-point variants ("3 1/2 inches" vs "3.5 in") — convert to decimals before computing.

Try it now​

The full length-converter runs in your browser at https://ztools.zaions.com/length-converter — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub