# A simple algorithm to calculate acreage from the number of square links

**Author:**Patrick Keane

**While the units of area based on the chain seem somewhat complex**, there is an underlying simplicity behind them. The method below is an illustration of the algorithm, adapted from *The Practical Surveyor* by Samuel Wyld, published in 1725.

Let us say you have a parcel of land containing an area of 307960 square links.

**a) Counting from the right, put a marker, perhaps a semi-colon, between the fifth and sixth character.**

We obtain: 3;07960.

The acreage is the number to the left of the semi-colon.

Our parcel contains 3 acres and a bit more.

**b) Multiply the number to the right of the semi-colon by 4 (the number of roods in an acre) to calculate the number of roods.**

07960 x 4

We obtain: 31840.

Once again we place a semi-colon between the fifth and sixth character counting from the right.

There is no sixth character, so we insert a zero.

We obtain: 0;31840

The number of roods is the number to the left of the semi-colon. There are no roods.

Our parcel contains 3 acres, 0 roods and a bit more.

**c) Multiply the number to the right of the semi-colon by 40 (the number of poles in a rood). **

31840 x 40

We obtain: 1273600

Once again we place a semi-colon between the fifth and sixth character counting from the right.

12;73600

The number of poles is the number to the left of the semi-colon.

**Our parcel contains 3 acres, 0 roods and 12 poles.** And, for any obsessives, an aditional 73600 hundred thousandths of a pole, roughly the area of a double garage.

This algorithm simply requires us to be able to count the digits of a number from right to left and to be able to multiply by four.

It is a triumph of combining the decimal system with the traditional measurements of land.