The sizes given are for the wingspan of the forewings, tip to tip, in millimetres. They are averages, butterflies do not usually vary much in size (they do all their growing as caterpillars) but there is some variation, sometimes caused by shortage of food for the caterpillar.

Butterfly Size description Average wingspan
Small Blue Small 24
Lulworth Skipper Small 26
Grizzled Skipper Small 27
Essex Skipper Small 28
Brown Argus Small 29
Dingy Skipper Small 29
Duke of Burgundy Small 30
Silver-studded Blue Small 30
Small Skipper Small 30
Green Hairstreak Small 33
Silver-spotted Skipper Small 33
Large Skipper Small 34
Small Copper Small 34
Common Blue Small 35
Holly Blue Small 35
Small Heath Small 36
White-letter Hairstreak Small 36
Purple Hairstreak Small 38
Adonis Small 38
Brown Hairstreak Small 38
Chalkhill Blue Small 38
Wood White Medium 42
Small Pearl-bordered Fritillary Medium 43
Gatekeeper Medium 44
Marsh Fritillary Medium 45
Wall Medium 45
Orange Tip Medium 47
Small White Medium 48
Speckled Wood Medium 49
Green-veined White Medium 50
Ringlet Medium 50
Meadow Brown Medium 53
Small Tortoiseshell Medium 54
Marbled White Medium 55
Comma Medium 58
Grayling Medium 58
Brimstone Large 60
Clouded Yellow Large 60
White Admiral Large 63
Dark Green Fritillary Large 66
Peacock Large 66
Large Tortoiseshell Large 67
Large White Large 67
Painted Lady Large 67
Red Admiral Large 70
Silver-washed Fritillary Large 74
Purple Emperor Large 80