An acre contains 160 perches. A perch measures 272.25 square feet, the same area expressed as 30.25 square yards, and in metric as 25.2929 square metres.
Those are definitions, not measurements. They do not move with the market, they do not differ between Colombo and Kurunegala, and no surveyor can change them. Everything that follows sits in the gap between the definition and the document, because the units written on a Sri Lankan land deed are not the units the law names, and that gap is where money quietly goes missing.
How the three units nest
The system is built on multiples of forty and four, which is why mental arithmetic on it fails so often.
| Unit | In perches | In square feet | In square metres |
|---|---|---|---|
| 1 perch | 1 | 272.25 | 25.2929 |
| 1 rood | 40 | 10,890 | 1,011.72 |
| 1 acre | 160 | 43,560 | 4,046.86 |
| 1 hectare | about 395.4 | , | 10,000 |
A hectare is 2.4711 acres. It is the only row that refuses to produce round numbers, which is exactly why plantation and agricultural extents, the ones quoted in hectares, are easy to mis-state.
Why the deed uses one system and the statute names another
The official units in Sri Lanka are metric. The Measurement Units, Standards and Services Act, No. 35 of 1995 adopts the International System of Units, and at section 12 it requires contracts, sales and dealings made in Sri Lanka to be expressed in the units it specifies.
Perches, roods and acres remain what deeds record, what boards outside plots advertise, and what buyers ask about on the telephone. Both systems therefore appear on paperwork, sometimes on the same sheet, an extent in perches on the deed, an area in square metres on the survey plan.
What that Act means for a particular instrument written in perches is a question of law. It is one for your notary or attorney, not for an estate agency. We set out where the position stands; we do not advise on it.
Reading an extent written as three numbers
Because the units nest, extents are commonly written as all three at once, largest first. An extent given as 0-2-15 is nought acres, two roods and fifteen perches. Two roods is 80 perches, so the whole thing is 95 perches.
Convert to a single number before you do anything else with it. Multiply acres by 160, roods by 40, add the loose perches, and work from that figure alone.
One acre, two roods and ten perches works out at 160 plus 80 plus 10, so 250 perches. That is 68,062.5 square feet, or 6,323.2 square metres. Anyone who rounds it down to one and a half acres has dropped ten perches, because an acre and a half is 240. Ten perches is a sixteenth of an acre, or 2,722.5 square feet, and at whatever rate per perch has been agreed it is ten perches of money.
Four places the arithmetic goes wrong
Rounding the perch. Treating a perch as 275 square feet rather than 272.25 looks harmless. Across a full acre it invents 440 square feet of land that is not there.
Confusing square yards with square metres. A perch is 30.25 square yards. It is 25.2929 square metres. The two figures sit next to each other in every conversion table, and swapping them overstates a twenty-perch plot by about 99 square metres.
Mixing units within one comparison. A plot advertised at 18 perches and one advertised at 500 square metres are not obviously different sizes until you convert. Eighteen perches is 455.3 square metres, so the second plot is the larger of the two by roughly a tenth.
Assuming a hectare is a tidy number of perches. It is about 395.4. A ten-hectare estate is therefore around 3,954 perches, not 4,000, and the difference is a plot of building land in its own right.
Converting a rate, not just an area
Land is advertised two ways at once, a total price and a rate per perch, and the two are supposed to reconcile. Where they do not, the extent sitting between them is the figure to check first.
Take a plot offered at fourteen perches with a stated rate per perch. The total ought to be fourteen times that rate. If a current survey then measures the parcel at 13.25 perches, the total has not changed but the rate has. The same money now buys three-quarters of a perch less, so the real rate is about 5.7 per cent higher than the one advertised.
That is worth doing before you negotiate rather than after, because the rate is the number you will compare against other plots and against what the street has sold for. A rate calculated from an unverified extent is not comparable to anything.
It is also worth noting which unit belongs to which thing. A building is quoted in square feet. The land beneath it is quoted in perches. Mixing the two into a single price per square foot for a house-and-land package is how two properties that look similarly priced turn out not to be.
What a perch is worth is a separate question
Knowing the size of a perch tells you nothing about the price of one. The published measure closest to that question is narrow. In Colombo District, the Land Valuation Indicator compiled by the Central Bank of Sri Lanka stood 10.6 per cent higher across the closing half of 2025 than it had a year before. The same Bank’s Land Price Index runs bi-annually, reaches back to 1998, and covers no district but Colombo.
That is a district-wide indicator. It moves with the aggregate, and no aggregate prices a particular road, a particular frontage or a particular access. A plot on a main road and a plot behind it can differ by more per perch than the index moved in a decade.
Nor does an index answer what a specific parcel would fetch. For that you need comparable evidence for the street, and A1 can give you a market appraisal built on it. A formal valuation is a separate instrument, prepared by a chartered valuer, and we refer that work out rather than attempt it.
Three extents, and they can all differ
A listing quotes an extent. A deed records an extent. A survey plan measures one. These are three separate assertions about the same ground, and they are not required to agree.
Only one of the three is produced by measurement, and that is the survey plan. Under the Survey Act, No. 17 of 2002, a plan prepared by a registered licensed surveyor is certified by that surveyor, and certified copies are deposited with the Surveyor-General within thirty days of certification. The Act also makes the Surveyor-General’s decision on any question of land surveying or mapping “final and conclusive”. Approval is a separate idea and belongs to a separate office: what you may then do with the parcel, build on it, subdivide it, is a matter for the relevant local authority, not for the surveyor who measured it.
Where a deed and a current plan disagree, the plan describes the land as it is and the deed preserves a historical belief about it.
Where to take this next
Do the conversion yourself before you negotiate, and do it in perches. If the per-perch rate and the total price do not reconcile, one of the two numbers is wrong and it is worth knowing which before an offer is on the table.
Then take the documents to a notary. Extent, boundaries and what a deed actually conveys are matters for a notary or an attorney, and no article, this one included, is a substitute for that advice. If you are buying or selling land in Colombo, Kandy, Gampaha, Kurunegala, Matara, Galle or Nuwara Eliya, A1 can talk you through what the extent means for price and marketing, and tell you plainly when the answer needs a surveyor instead.