Length Converter
Instantly convert Length between SI and common engineering units including Meter (m), Kilometer (km), Decimeter (dm), Centimeter (cm). No formula lookup required.
Convert
About
Value × conversion factor to SI base (temperature uses affine offset), then restored to target unit.
Bidirectional conversion with unit swap supported.
How to use
- Enter the value to convert in the Value box.
- Pick the source and target units from the From / To dropdowns.
- Click Convert; the result shows below. Use ⇅ to swap units.
Formula notesUnit conversion (length): 长度：1 km = 1000 m，1 in = 25.4 mm，采用线性比例换算。
Formula · Worked Example · Knowledge
Formula
Length conversion uses the metre (m) as base; each unit's factor $a$ satisfies $\text{value}_{\text{SI}}=a\times\text{value}_{\text{unit}}$. E.g. $1\ \text{in}=0.0254\ \text{m}$, $1\ \text{ft}=0.3048\ \text{m}$, $1\ \text{mi}=1609.344\ \text{m}$. Conversion:
$$x_{\text{target}}=\frac{a_{\text{src}}}{a_{\text{target}}}\,x_{\text{src}}$$
$$x_{\text{target}}=\frac{a_{\text{src}}}{a_{\text{target}}}\,x_{\text{src}}$$
Worked Example
Convert $1\ \text{m}$ to inches:
$$x_{\text{in}}=\frac{1}{0.0254}\approx39.37\ \text{in}$$
So $1\ \text{m}\approx39.37\ \text{in}$; $1\ \text{ft}=12\ \text{in}=0.3048\ \text{m}$.
$$x_{\text{in}}=\frac{1}{0.0254}\approx39.37\ \text{in}$$
So $1\ \text{m}\approx39.37\ \text{in}$; $1\ \text{ft}=12\ \text{in}=0.3048\ \text{m}$.
Key Points
- SI base unit of length is the metre (m); decimal multiples: km, cm, mm, μm, nm.
- Imperial in/ft/yd/mi have fixed ratios to SI: 1 in = 25.4 mm, 1 ft = 304.8 mm, 1 mi = 1609.344 m.
- This tool covers 13 length units with bidirectional conversion and unit swap.