How do i find out....

[hammerman]

The frame size on my push bike that im selling ?

[snags]

Measure from centre of bottom bracket to top of seat tube (also give measurement from centre of seat tube, along top tube to centre of headtube).

[shoota]

3 measurements:
centre of headtube to centre of seat tube
centre of bottom bracket to top of seat tube
centre oc bottom bracket to rear spindle

(my son builds bikes.....)