Ramstein-dh Get two old spokes and screw 12mm nipples on to each until the spoke is at the top of the nipple. Each spoke should be cut to 200mm in length.
Lay your rim on a long ruler with mm markings and place the two spokes in the rim at opposite ends and pull the nipples into the nipple seat. Measure the distance between the end of the two spokes and add 400mm (the length of the two spokes). A slight different but gives the same result is given on sheldon Borwn's site in the link below.
You can download spocalc from sheldon brown's site as well- an alternative to DTswiss version. It's a excel spreadsheet and works quite well.
http://www.sheldonbrown.com/rinard/spocalc.htm
Lay your rim on a long ruler with mm markings and place the two spokes in the rim at opposite ends and pull the nipples into the nipple seat. Measure the distance between the end of the two spokes and add 400mm (the length of the two spokes). A slight different but gives the same result is given on sheldon Borwn's site in the link below.
You can download spocalc from sheldon brown's site as well- an alternative to DTswiss version. It's a excel spreadsheet and works quite well.
http://www.sheldonbrown.com/rinard/spocalc.htm