For off the peg, one size fits all solutions, the size will be adjustable in the nape area of the wig. Popular adjustment methods are straps, velcro and clips. Different wig ranges will have slight variations in their standard base size. Trying on a number of wigs is the best way to check for a secure and comfortable fit. The closeness of the fit will vary between individuals due to differing scalp shapes.

Typical wig ranges will have a standard fit (52-55cm cap) with adjustable straps for comfort, tightening and loosening. Petite wig ranges, though more restricted in styles and colours, will cater for those with smaller head sizes (50-52cm cap).
For an accurate wig fitting one should be measured from the centre point of the hair line to just above the occipital bone returning to the initial central hairline point.

Custom-made wigs, also referred to as hair systems, will provide a bespoke fit produced by taking a mould of the head. From this template a lightweight membrane is produced creating a vacuum type fit with the scalp, referred to as a second skin.