There are two ways to measure how many rails you require. One is simply to measure each wall, in metres, add them all together, and divide by 2, (each rail is 2m long). When doing this you MUST add between 5 and 10% to the total, otherwise on the last section of wall you'll be fixing a long line of short offcuts together.
The preferred method is take each wall as a separate section. Say your first wall is 4.5m, you will need 1x 2m and 1x 3m rails leaving .5m of offcut. When measuring the next wall and it's, say 3.5m, you will need 1 whole 3m rail and the .5m offcut. As you measure each wall, keep a note of the offcut size so you can use it where appropriate. If a wall is 2.2m long it is best to use a 3m length cut to the right size rather than a 2m rail with a short .2m off cutas a minimum of 2 fixings is required for any one length
We recommend using two hangers and hooks per picture, so estimate the likely number of pictures you'll be displaying at any one time and multiply by two. Bear in mind that hangers and hooks are always readily available so you can always order a few more if you need to. There is no minimum order or restrictions as everything is available individually. If you have more pictures than you could ever hang at once, and they're mostly of an average size, allow four hangers per rail. You may want twice as many hooks than hangers as you can hang pictures one above the other on the same hangers.