Most of us wear the wrong size without realising it, and pay for it with a long, uncomfortable day. Measuring at home takes a tape and a mirror.

Two measurements

Wear a light, unpadded bra and stand straight in front of a mirror.

• Underbust: wrap the tape directly under your bust, firm and parallel to the floor. Round to the nearest even number — that is your band.
• Bust: wrap it around the fullest part without pressing. The difference gives the cup: about 12 cm is a B, 15 cm a C.

Signs the size is wrong

• The band rides up at the back instead of staying level.
• The cup gapes, or digs in under clothes.
• The straps leave marks on your shoulders.
• You adjust the bra all day.

The band and cup rule

Support comes from the band, not the straps. If the band feels loose, go down a band and up a cup: an 80C is closer to a 75D than you would think. Start on the loosest hook and move inwards over time.

Measure again every six months, and after any change in weight.