Most units have one value and a conversion you can look up. The dunam has several, all of them correct in their own place and time, and the document in front of you almost never says which it means.
How many square metres in a dunam
1,000 m²
That is the metric dunam, used today in Jordan, Palestine, Syria, Lebanon and Turkey, and it is exactly a tenth of a hectare. An Ottoman-era document means about 919 m² instead, and Iraq means 2,500 m².
The three readings
1,000 m² — the metric dunam. Standardised during the 1920s and 1930s and now the ordinary meaning across the Levant and Turkey. Exact by definition, not by measurement, which is why it converts so cleanly: ten to the hectare, a hundred to the square kilometre.
About 919.3 m² — the Ottoman dunam. The value in use in Ottoman Palestine and into the early Mandate period, derived from 1,600 square cubits. It is eight per cent smaller than the modern one, which is small enough to look like rounding and large enough to matter over a few hundred dunams.
2,500 m² — the Iraqi dunam. Two and a half times the metric figure. A converter that assumes 1,000 will report an Iraqi plot as less than half its actual size, and the answer it gives looks perfectly reasonable.
The spread is not an accident of translation. The dunam began as the area a man with an ox could plough in a day — a genuine quantity that depends on the ground, the animal and the season, and therefore on the province. The Ottoman state inherited a unit that already varied, and the metric redefinition later fixed it in some countries and left it alone in others.
What it is not
Not a feddan. The Egyptian feddan is 4,200.833 m², more than four dunams. English writing about Egyptian agriculture frequently prints acre where the source said feddan, and the two differ by about four per cent — a feddan is roughly 1.038 acres. Both substitutions are common and neither is harmless in a table of areas.
Not an acre. An acre is 4,046.856 m², so a dunam is about a quarter of one, or 0.247 to be exact enough for anything. Neither number is round, which is what you expect from two units that grew up unrelated.
Not a hectare, but very nearly a tenth of one. This is the relationship worth memorising, because it is exact: 10 dunams to the hectare, 100 to the square kilometre. Once you have it, the metric dunam stops needing a converter at all.
Working out which one a document means
If the paper gives dimensions as well as an area, the arithmetic settles it. Multiply the sides, divide by the stated number of dunams, and see which of the three values the answer lands near. A plot described as 40 by 50 metres and “two dunams” is using the metric one; the same plot called “four dunams” is not describing the same ground.
Where there are no dimensions, the date and the country decide it. A deed written in Palestine before 1928 is Ottoman; one written after is metric. An Iraqi document is 2,500 m² whatever its date. This is one of the few cases where knowing when a paper was written is genuinely part of reading it.
The failure mode to watch for is silence. No converter announces which dunam it used, including this one — the area converter here uses the metric 1,000 m² dunam and has no entry for the Iraqi or the Ottoman value. For those, convert by hand: multiply by 2,500 or by 919.3 to get square metres, then convert onwards from there.
The conversions worth having
1 dunam = 1,000 m² = 0.1 hectare = 0.247 acre.
1 hectare = 10 dunams = 10,000 m² = 2.471 acres.
1 feddan = 4,200.833 m² = 4.2 dunams = 1.038 acres.
1 acre = 4,046.856 m² = 4.047 dunams.
1 km² = 100 hectares = 1,000 dunams.
The last one is the sanity check that catches most mistakes. Land reported in the news in dunams is easiest to picture by dividing by a thousand and reading the result as square kilometres: 3,000 dunams is three square kilometres, which is a shape you can hold in your head in a way that four figures never is.
The short version
A dunam is 1,000 square metres unless something tells you otherwise, and two things commonly do: an Iraqi document, where it is 2,500, and a pre-metric deed, where it is about 919. A feddan is not a dunam and an acre is not a feddan. When the paper gives dimensions, trust the arithmetic over the label.
The converter here runs in your browser, on numbers that go nowhere, which mostly matters because it means you can check a figure from a document you would rather not paste into somebody’s website.