Square Rod (sq rd)

US & ImperialTraditional unit (still used in some regions)

30.25 square yards (25.29 m²), also called a perch. 160 square rods make an acre.

1 square rod = 25.29285264 square meters (exactly).

About the square rod

Perch is the older name for this small square, and it traces back to the Roman pertica, a measuring pole. The word rod became the preferred surveyors' term in England, where land measurers carrying rods, poles or knotted cords were in demand after Henry VIII took over church estates in 1536. A square rod is the square on a rod of 16.5 feet, which works out to 272.25 square feet, or 30.25 square yards.

The odd-looking number makes sense through the acre. Edmund Gunter's 66-foot chain is four rods long, so a square chain holds 16 square rods, and ten square chains make an acre. That means 160 square rods fill an acre, and a rood holds 40. Metric equivalents are about 25.29 square meters, a little under the floor area of a small garage. Rods and perches turned up in deeds, tax records and plot descriptions for centuries, and a few English-speaking regions still quote small building plots in perches.

Sources: Wikipedia: Rod (unit); Wikipedia: Chain (unit); Wikipedia: Acre

Square Rod conversion chart

1 square rod expressed in every other area unit:

More US & Imperial units

• square inch (area)
• square foot (area)
• square yard (area)
• acre (area)
• square mile (area)
• square chain (area)
• inch (length)
• foot (length)
• yard (length)
• mile (length)
• thou (length)
• league (length)
• furlong (length)
• chain (length)
• rod (length)
• link (length)

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