One tunnland is 0.49366 hectares, or 4,936.6 square metres. It is the traditional Swedish measure of farmland, and it is very nearly half a hectare — close enough that older Swedish acreage figures can be halved for a quick estimate.
About the units
The tunnland is one of the more logical old land units: it was the area that could be sown with one tunna, a barrel, of seed grain. That made it a measure of productive capacity rather than of geometry, which is why it varied by soil quality before standardisation. It was fixed at 14,000 square Swedish ells — 56,000 square Swedish feet, the Swedish foot being half an ell — which came to 4,936.6 m², and it was subdivided into 32 kappland. Sweden abolished it for official use during metrication in the late nineteenth century, but it persisted in farming vocabulary for generations and appears throughout historical land records, parish registers and estate inventories.
The exact factor
One tunnland is 4,936.6 m², so 1 tunnland = 0.49366 hectares and 1 hectare = 2.02569 tunnland. The near-half relationship is the practical takeaway: doubling a tunnland figure gives hectares to within 1.3 per cent. In acres, one tunnland is 1.2199, so it is also close to a quarter more than an acre. The kappland, at 154.3 m², is the subdivision that appears in older records for garden plots and small parcels.
Where you meet this conversion
Swedish historical research of every kind: genealogy, local history, agricultural history and property law. Estate inventories, farm sale records and parish agricultural returns from before about 1880 give holdings in tunnland, and comparing them to modern hectare figures for the same land is a standard task. Some Swedish farmers still use the word informally. Finnish records use the closely related tynnyrinala, which had a slightly different value, so a Finnish source cannot be converted with the Swedish factor.