How to find what bed size you have and also.
How to measure what headboard fits your bed.
First, what size bed do you have? choose it from the drop down:

75cm headboard is equivalent to a small single size 2ft 6` bed
90cm headboard is equivalent to a standard single size 3ft bed
100cm headboard is equivalent to a special large single size 3ft 3` bed
107cm headboard is equivalent to a special large size 3ft 6` bed

120cm headboard is equivalent to a small double size 4ft bed

135 / 140cm headboard is equivalent to a standard double size 4ft 6 bed

150cm headboard is equivalent to a standard king size 5ft bed
165cm headboard is equivalent to a special large king size 5ft 6` bed

180cm headboard is equivalent to a standard superking size 6ft bed
200cm headboard is equivalent to a special superking size 6ft 6` bed

Bed headboard fixing hole measurements.

Also some helpful information is the distance between the headboard fixing holes on your divan bed base

3ft Single headboard = distance between holes = 24" = 610mm
4ft Small Double headboard = distance between holes = 36" = 915mm
4ft 6" Double headboard = distance between holes = 42" = 1067mm
5ft King Size headboard = distance between holes = 48" = 1219mm
6ft Super King Size headboard = distance between holes = 60" = 1524mm