Some common guitar scale lenghts

22.50" / 571.50 mm Fender Jazzmaster/Jaguar
23.50" / 571.50 mm Gibson Byrdland
24.00" / 609.60 mm Fender Duo-Sonic/Mustang
24-9/16" / 623.88 mm Gibson-style guitar (See note below)
24.75" / 628.65 mm Rickenbacker, Guild-style guitar
25.00" / 635.00 mm PRS, National-style guitar
25.34" / 643.64 mm Martin standard steel string guitar
25.40" / 645.16 mm Martin Dreadnought or OM steel string guitar
25.50" / 647.70 mm Fender-style-guitar, Gibson acoustic guitar
25.59" / 650.00 mm Typical classical guitar
25-5/8" / 650.88 mm Guild acoustic guitar
27.67" / 702.82 mm Baritone guitar
30.00" / 762.00 mm Short scale bass guitar
32.50" / 825.50 mm Medium scale (Rickenbacker-style) bass guitar
34.00" / 863.60 mm Long scale (Fender-style) bass guitar

For an explanation of the Gibson scale length changes over the years see www.stewmac.com