Everyday Unit Converter
Convert the measurements you meet in recipes, travel, shopping, and weather reports. Switch between length, weight, and temperature, then choose the units you need.
Sri Lankan land units
Land here is priced per perch and written on deeds as acres, roods and perches, none of which step in tens. One perch is 272.25 square feet; forty perches make a rood; four roods make an acre, so an acre is 160 perches or 43,560 square feet.
That is why a plot written as 1-2-20 on a deed means one acre, two roods and twenty perches - 260 perches in total, since the acre alone is 160 - and cannot be read as 1.22 acres. The area converter handles all of these directly.
| Unit | In perches | In square feet | In square metres |
|---|---|---|---|
| 1 perch | 1 | 272.25 | 25.29 |
| 1 rood | 40 | 10,890 | 1,011.71 |
| 1 acre | 160 | 43,560 | 4,046.86 |
| 1 hectare | 395.37 | 107,639 | 10,000 |
Everything converts through one base unit
Converting directly between every pair of units would need a factor for each combination. Routing through a single base unit instead -- metres for length, kilograms for weight -- means one factor per unit, and any pair can be reached by converting in and then out.
It also keeps the factors exact. An inch is defined as exactly 0.0254 metres and a pound as exactly 0.45359237 kilograms, so these are definitions rather than measurements and carry no error of their own.
| Unit | In base units | Status |
|---|---|---|
| 1 inch | 0.0254 m | Exact by definition |
| 1 foot | 0.3048 m | Exact by definition |
| 1 mile | 1,609.344 m | Exact by definition |
| 1 pound | 0.45359237 kg | Exact by definition |
| 1 ounce | 0.028349523125 kg | Exact by definition |
Temperature is the exception
Length and weight scales share a zero point, so converting is a single multiplication. Temperature scales do not: 0 degrees Celsius and 0 degrees Fahrenheit are different temperatures, so the conversion needs an offset as well as a ratio.
That is why a temperature difference converts differently from a temperature. A rise of 10 degrees Celsius is a rise of 18 degrees Fahrenheit, not 50 -- the ratio applies to the interval, the offset does not.
| Point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 25 | 77 | 298.15 |
| Colombo on a hot day | 33 | 91.4 | 306.15 |
| Water boils | 100 | 212 | 373.15 |
Where the units actually turn up in Sri Lanka
Sri Lanka is metric, but imperial units persist in specific corners of daily life, which is usually why a conversion is needed at all.
- Height is commonly given in feet and inches despite metric medical records.
- Land is measured in perches and acres rather than square metres.
- Screen and tyre sizes are quoted in inches.
- Recipes from overseas sources arrive in ounces, pounds, and Fahrenheit.