Add on Sash-Weight Calculator
Working out exactly how much weight to add can be tricky, and it's one of the questions we get the most phone calls about. So we've put together this little calculator to help you estimate what's needed on each side.
How much weight do you need to add?
Weigh the sash once it's out, and this works out what each side needs and how many Add-On Weights to buy.
This is the trade trusted method. Eyeballing it, or trying to do a complicated calculation from glass weight and window dimensions, is never going to be as accurate as actually weighing the sash. In our opinion, weighing it on a set of scales is the only way to get this right.
Before you weigh in
Take out the parting bead and pocket to expose the cavity, untie the cord, and lift the weight clear. Then weigh the sash itself on a set of bathroom or kitchen scales and enter it below.
On the top sash, the weights need to be slightly heavier than the sash itself. This makes sure the sash holds up in the head of the frame and doesn't fall down by itself.
Weigh the sash on bathroom or kitchen scales.
Tell us what's already on each side and we'll work out the top up.
Older cast weights are often stamped with their weight in pounds. Sometimes this is using Roman numerals rather than kg, for example VII for 7lb. Multiply the pounds by 0.45 to convert to kg.
Weight needed per side
0 kg
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add on weights per side
A note on lead safety: sash weights are usually made from lead, cast iron or a lead alloy, and older sash windows may have been painted with lead based paint. Take appropriate precautions when handling weights or when sanding or disturbing painted timber, see SafeWork NSW's guidelines on lead work before you begin.
