Measurement Trivia for Old Deeds A chain is a measure used by engineers and surveyors, being twenty yards in length. Black's Law Dictionary (4th Edition) at pate 290. 1 Chain is equal to 100 links, or 4 perches, or 4 rods, or 4 poles or 66 feet. A link is a linear measure equal to 7.92 inches 25 links equals 16 1/2 feet or 1 perch or 1 rod or 1 pole. Additional terms that you may encounter in old deeds. A perch is a linear measure equal to 16 1/2 feet. Old deeds also use perch as a square measure and they did not always use the word square immediately preceding the word perch. You have to determine what they meant by context in which the work is used. If the deed read "Containing 66 acres and 43 perches", the scrivener meant square perches even thought he did not specifically write the word square. There are 160 square perches to 1 acre. An acre is 43,560 square feet. Rod is a linear measure equal to 16 1/2 feet. Rods are also used as square measurement same as perches. (see above) Pole is a linear measure equal to 16 1/2 feet. Poles are also used as square measurements same as perches. (see above) 16 square perches, rods or poles equals 1 square chain 10 square chains equals one acre 160 square perches, rods, or poles equals 1 acre 640 acres (one section) equals 1 square mile. Other trivia: 80 chains, 320 perches, 320 rods, 320 poles, or 5,280 feet equals one mile. Hope this helps. Leslie Potter P.S. I do not do metric!