Length Converter

How length conversion works

All lengths are converted through meters using exact, internationally agreed factors — the inch, foot, yard, and mile have been defined in metric terms since 1959, so there is no approximation in the math itself, only in the rounding you choose.

result = value × meters(from) ÷ meters(to)

Exact factors

Worked examples

• 10 meters to feet — 10 ÷ 0.3048 = 32.81 ft.
• 5 km to miles — 5,000 ÷ 1,609.344 = 3.11 mi.
• 6 ft to centimeters — 6 × 30.48 = 182.88 cm.

When you need to convert lengths

• Travel — reading road signs in kilometers when you think in miles, or the reverse.
• DIY and building — following a plan in millimeters while your tape measure reads inches.
• Height — turning 5 ft 10 in into 178 cm for a form or a fitness app.
• Screens and print — matching a diagonal in inches to centimeters, or margins in mm to inches.

Quick reference

A handful of round conversions cover most everyday needs: 1 inch ≈ 2.5 cm, 1 foot ≈ 30 cm, 1 meter ≈ 3.28 ft, and 1 mile ≈ 1.6 km (so 5 miles ≈ 8 km). These are close enough for estimates; the calculator applies the exact 1959 factors when precision matters.

Centimetres to feet and inches for height

Height is the single most common reason people convert centimetres, and it needs two steps because feet and inches are a mixed unit. Divide by 2.54 to get total inches, then split that into whole feet and the remainder:

total inches = cm ÷ 2.54  ·  feet = ⌊total ÷ 12⌋  ·  inches = total − feet × 12

"American height" means exactly this format — the US and UK state height in feet and inches, while most of the world uses centimetres on the same forms.

Metric prefixes and the very large and very small

Metric units are powers of ten from the metre, so these are decimal shifts rather than lookups. One centimetre is 0.1 decimetres (dm), 0.0001 hectometres (hm), and 0.00001 km.

Hands: how horse height is measured

A hand (hh) is exactly 4 inches, or 10.16 cm, and it is still the standard for horse height measured at the withers. Hands use a peculiar notation: the digit after the decimal point counts inches, not tenths, so it only ever runs 0–3. "15.2 hh" means 15 hands and 2 inches — that is 62 inches, or 157.5 cm. It does not mean 15.2 × 10.16.

Why cm does not convert to cm², m³, acres, or hectares

A centimetre is one dimension. Area needs two and volume needs three, so there is no factor from cm to cm² — you need the other measurements first.

• Area — multiply two lengths. A 30 cm × 20 cm panel is 600 cm². One acre is 4,046.86 m²; one hectare is exactly 10,000 m². Work these out with the area calculator.
• Volume — multiply three. A 30 × 20 × 10 cm box is 6,000 cm³, which is 0.006 m³ (CBM) or about 0.212 ft³ (CFT). Shipping quotes use CBM, and it is always a volume, never a length. The volume calculator handles the shapes.

So "cm to CBM" is really "what is the volume of a box this size", and it needs all three sides.

Centimetres to pixels depends on the screen

A pixel is not a fixed length — it depends on pixel density, so the same 1 cm is a different number of pixels on every device. The conversion only exists once you fix a DPI:

pixels = cm ÷ 2.54 × DPI

CSS solves this by defining a reference: in CSS, 96 px is one inch by definition, which makes 1 cm = 37.8 CSS pixels regardless of hardware. Print work uses the real density instead — at 300 DPI, 1 cm is 118 px.

"cm to kg" and "cm to grams" are not conversions

Centimetres measure length and kilograms measure mass, so nothing connects them directly. These searches normally mean one of two things: you have a height and a weight and want BMI, which the BMI calculator gives you from both figures; or you have an object's dimensions and want its mass, which needs the material's density — volume first, then mass = volume × density. Pressure units such as atmospheres and bar are the same story: they need a force and an area, not a length.

For weights, areas, and volumes in one place, use the unit converter.