CADGISHow to use the unit converter
- Choose a category: Length, Area or Angle.
- Type a value, then pick the unit you have and the unit you want. The result appears instantly, with the same value shown in every unit of the category below it.
- Use Swap to reverse the direction, Copy to copy the result, and Clear to start again.
- Leave Decimal places blank for automatic precision (up to 12 significant digits), or set a fixed number of places.
For DMS, enter degrees, minutes and seconds separated by spaces or symbols, for example 12° 34' 56.7", 12 34 56.7 or -12:34:56. Minutes and seconds must be less than 60.
Length units
| Unit | In metres (exact) | Notes |
|---|---|---|
| Metre (m) | 1 | SI base unit |
| Kilometre (km) | 1 000 | |
| Centimetre (cm) | 0.01 | |
| Millimetre (mm) | 0.001 | Common in CAD drawings |
| Foot (ft) | 0.3048 | International foot, defined 1959 |
| Inch (in) | 0.0254 | 12 inches = 1 foot |
| Chain (ch) | 20.1168 | Gunter's chain = 66 ft = 100 links |
| Link (lk) | 0.201168 | 1/100 chain = 7.92 in |
| US survey foot | 1200 / 3937 ≈ 0.304800609601 | Used in older US state plane systems |
The chain and link come from Gunter's chain of 1620, still found on old cadastral plans and deeds. Ten square chains make one acre, which is why the acre converts so neatly to chains.
Area units
| Unit | In square metres (exact) | Notes |
|---|---|---|
| Square metre (m²) | 1 | SI unit |
| Square kilometre (km²) | 1 000 000 | 100 hectares |
| Hectare (ha) | 10 000 | 100 m × 100 m |
| Acre (ac) | 4 046.856 422 4 | 4 840 yd² = 10 square chains |
| Square foot (ft²) | 0.092 903 04 | Based on the international foot |
| Cent | 40.468 564 224 | 1/100 acre, used in South India |
| Guntha | 101.171 410 56 | 1/40 acre = 1 089 ft², used in western and southern India |
Cent and guntha are both defined from the acre, so 40 guntha = 100 cent = 1 acre exactly. One guntha is 2.5 cent.
Angle units
| Unit | Full circle | Right angle | Notes |
|---|---|---|---|
| Degree (°) | 360 | 90 | Decimal degrees, used by GIS and GPS |
| Radian (rad) | 2π ≈ 6.283185 | π/2 ≈ 1.570796 | Used in formulas and programming |
| Gon (gradian) | 400 | 100 | Used by total stations and in European surveying |
| DMS | 360° 00' 00" | 90° 00' 00" | Degrees, minutes, seconds: 1° = 60', 1' = 60" |
Conversion formulas
result = value × (factor of source unit) ÷ (factor of target unit)
Every unit is stored as its exact factor to the base unit of its category (metre, square metre or degree), so each conversion is a single multiplication and division with no chained rounding. Angles use: radians = degrees × π / 180, and gon = degrees × 10 / 9.
Worked examples
- 1 chain to metres: 1 × 20.1168 = 20.1168 m
- 2.5 acres to hectares: 2.5 × 4046.8564224 ÷ 10000 = 1.011714 ha
- 3 guntha to square feet: 3 × 1089 = 3267 ft²
- 1000 ft in US survey feet: 1000 × 0.3048 ÷ (1200/3937) = 999.998 ft (US)
- 100 gon to degrees: 100 × 0.9 = 90°
- 1 radian to DMS: 57.295780° = 57° 17' 44.81"
Frequently asked questions
What is the difference between the international foot and the US survey foot?
The international foot is exactly 0.3048 m. The US survey foot is 1200/3937 m, about 0.3048006 m. The difference is 2 parts per million, which matters over long distances and in state plane coordinates. The US officially retired the survey foot for new work at the end of 2022, but older plans and coordinate systems still use it.
How many square feet are in a guntha?
One guntha is 1 089 square feet, which is 1/40 of an acre or about 101.17 square metres.
How many degrees is one gon?
One gon (gradian) is 0.9 degrees. A full circle is 400 gon and a right angle is 100 gon, which is why many total stations offer it.
Why does the result sometimes show many decimal places?
In automatic mode the converter shows up to 12 significant digits and trims trailing zeros, so exact conversions such as 1 ft = 0.3048 m stay short while small values keep their precision. Set a fixed number of decimal places if you need rounded output.