Hello, I am not sure how you are calculating the numbers, so..... If memory serves me correctly you should be taking the percentage of the long side of the PWB (10.98) to get the allowable. In this case .75% of 10.98" would allow for .082", or for the 1.5% on the 10.98" would allow for .165". This would be the criteria for the long side. Then you get into the fact that the IPC issues guidelines, as such design or process or technology can dictate you use a different criteria. In a previous life we used 1% until we started using technology and machinery which called for us to tighten up to a .065%. Hope this helps Richard At 01:58 PM 7/27/01 EDT, you wrote: >>>> Technetters, IPC-6012 indicates that the allowable bow and twist of PCB is .75% for SMT and 1.5% for others. I have a PCB that is exhibits bow and twisting and I want to make sure that it is inside of the acceptable parameters. The board size is 10.98" x 6.81", so the allowable bow and twist would be: .75%- 0.561" 1.5%- 1.122" Are my calculations/assumptions correct? Any and all advise would be truly appreciated. Regards, <<<<<<<< --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------