📏 Length Precision Converter & Architectural Scale

Convert between any length units instantly — from nanometers to parsecs. Supports metric, imperial, architectural tape fractions (1/64"), and astronomical units. Meets NIST SP 811 and the 1959 International Yard Agreement standards. Natural language phrases like "5 feet 10 inches in cm" and compound expressions are handled automatically.

Length conversion calculates equivalent linear distance across metric, imperial, and astronomical systems. Defined by the 1959 International Yard and Pound Agreement and NIST Special Publication 811, 1 inch equals exactly 25.4 millimeters (2.54 cm), 1 foot equals exactly 0.3048 meters, and 1 meter equals approximately 3.2808399 feet.

Metrological Standards & Base Equation

1 meter = 3.2808399 feet. 1 inch = exactly 25.4 millimeters (1959 International Yard Agreement). 1 kilometer = 0.6213712 miles.

All linear conversion factors on this platform strictly comply with NIST Special Publication 811 (Guide for the Use of the International System of Units), the BIPM SI Brochure (9th Edition), and the 1959 International Yard and Pound Agreement (codifying 1 yard = 0.9144 m and 1 inch = 25.4 mm). Astronomical distances are grounded in the International Astronomical Union (IAU 2012) resolution defining 1 AU = 149,597,870,700 m.

Primary References: NIST SP 811 (2008 Edition) · BIPM SI Brochure (2019) · Standards Directory

Supported Length Units (23 Total)

Length Unit Definitions and Scaling Factors
Unit Symbol Unit Name System Equivalent in Meter
nm Nanometer Metric 1 nm = 1.000000e-9 m
µm Micrometer Metric 1 µm = 0.000001 m
mm Millimeter Metric 1 mm = 0.001 m
cm Centimeter Metric 1 cm = 0.01 m
dm Decimeter Metric 1 dm = 0.1 m
m Meter Metric SI Base Unit (1 m)
km Kilometer Metric 1 km = 1000 m
in Inch Imperial 1 in = 0.0254 m
ft Foot Imperial 1 ft = 0.3048 m
yd Yard Imperial 1 yd = 0.9144 m
mi Mile Imperial 1 mi = 1609.344 m
nmi Nautical Mile Other 1 nmi = 1852 m
furlong Furlong Imperial 1 furlong = 201.168 m
chain Chain Imperial 1 chain = 20.1168 m
rod Rod Imperial 1 rod = 5.0292 m
hand Hand Imperial 1 hand = 0.1016 m
cubit Cubit Other 1 cubit = 0.4572 m
ly Light Year Scientific 1 ly = 9.461000e+15 m
AU Astronomical Unit Scientific 1 AU = 149600000000 m
pc Parsec Scientific 1 pc = 3.086000e+16 m
LD Lunar Distance Scientific 1 LD = 384400000 m
R☉ Solar Radius Scientific 1 R☉ = 695700000 m
R⊕ Earth Radius Scientific 1 R⊕ = 6371000 m

Popular Length Conversions

Meter to Feet

m → ft — standard construction & height conversion

Kilometer to Miles

km → mi — road distance & travel planning

Inches to Centimeter

in → cm — screen sizes & clothing dimensions

Feet to Meters

ft → m — real estate & architecture

Centimeter to Inches

cm → in — product dimensions & body measurements

Conversion Guides & Step-by-Step Formulas

Step-by-step formula derivation, worked examples, and quick lookup tables.
Step-by-step formula derivation, worked examples, and quick lookup tables.

Common Use Cases

  • Construction & architecture (ft↔m)
  • Travel & navigation (km↔mi)
  • Clothing & body measurements (in↔cm)
  • Scientific research (nm, μm, ly)
  • Real estate & property (ft↔m, ac↔ha)

Frequently Asked Questions

How do I convert meters to feet?

Multiply the length in meters by 3.2808399 to calculate decimal feet. For example, 10 meters × 3.2808399 = 32.81 feet. To convert into feet and inches, multiply the decimal remainder by 12.

How many inches are in a centimeter?

One centimeter equals exactly 0.393700787 inches. Conversely, one inch is internationally defined as exactly 2.54 centimeters (25.4 millimeters).

What is the difference between an international foot and a US survey foot?

An international foot is defined as exactly 0.3048 meters. The historic US survey foot equals 1200/3937 meters (approx. 0.30480061 meters). NIST officially deprecated the US survey foot on January 1, 2023, standardizing all US mapping on the international foot.