your local bike shop (LBS) should have a spoke gauge that can tell you the answer if they are straight gauge...usually 14, 15 or 16. If you have butted spokes then you may need a micrometer or caliper to get actual dimensions of mid vs. end and then go to Sheldon Brown's website for conversion. Hope this helps. BTW. Anytime you're getting a wheel built you should get at least 2-3 extra front and rear (both sides) spokes and tape them to your seat stay, chain stay or front fork.