You won't get far doing DIY if you can't measure properly but it's actually surprisingly easy to get measurements wrong, wasting time and materials in the process.

So, apart from double, even triple, checking your measurements, what else will help you get it right first time?

Accurate measuring is vital before you order or buy materials because it helps you plan the job properly. Most things are sold in metric quantities these days, but if you're not comfortable working in metres, millimetres, etc, stick to imperial and convert it if you need to, or get the shop to convert it for you.

The trick is to only work in one system to avoid confusion and inaccuracies.

Having someone there to help you measure and check your measurements always helps, especially if you're measuring a large area, doing a complicated calculation or using a long tape measure.

With a large area, it helps to drive in pegs as markers if possible. If you're measuring an irregular shape, the easiest approach is to divide it into rectangles and squares, measure these and then add them together for your total.

Whatever you're measuring, make sure you work in good light and have everything you need at hand. And remember to allow extra materials for mistakes and wastage. It's hard to generalise how much because it varies from job to job and material to material, but 10 per cent is often enough.

The tools for the job

■ Straightedges (either plain or calibrated) are useful when measuring and marking. They can be used to draw straight lines, test their straightness and transfer measurements accurately across an area longer than the ruler you're using. You can also use them to check if a surface is flat. To check that the straightedge is itself accurate, take hold of it at one end and look down it to see if it curves.

■ Bench rules are another useful measuring tool, and rigid ones can be screwed on to the top of a workbench, hence the name. Flexible ones are ideal for measuring curves, though it's better to use a fabric tape measure for tight curves.

■ A metal ruler, preferably a long one, is a must for DIY. Unlike plastic rulers, you can't score into them accidentally when using a craft knife. They also have the advantage of being more rigid than plastic. The main problem with them is that they can slip on smooth surfaces, so make sure you spread your fingers out along the length of the ruler to hold it down well. Many steel rulers are calibrated all the way along so you can use the end of them for marking, as well as the length, which makes measuring and marking easier.

Marking out

When marking, felt-tip pens are easy to see but they're too thick to be really precise. For this, you need a pencil - a sharp one. However, pencil lines can be hard to make out on some surfaces and can get erased in the process of cutting, when using a water-cooled diamond-wheel tile cutter, for example.

When you're marking a surface before cutting it, use a craft or marking knife if possible. On something like wood, these cut into the fibres slightly and enable you to get a more precise cut.

Remember, mistakes can be costly.

Q&A

How do I mark a length of, say, wood out into equal parts?

Probably the easiest answer is to place your ruler diagonally across the wood and then decide how many divisions you want. Ensure that the end of the ruler is level with the edge of the wood and the divisions should fall equally.


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