Bicycle Mechanics - Newbie wheel builder looking for help

Hi all, I am trying to calculate the spoke length on my new set of rims and used hubs. I bought a set of Bontrager Race wheels that had Bontrager by Chris King hubs on them. They are 24 radial spoked on the front and 28 with 3x drive side and radial on non drive. On the rear rim one of the eyelets was pulling out so I decided to take the challenge and put on some new rims. I bought a pair of Sun Equalizer 21 rims. It was hard to find 24 and 28 hole rims. I am now trying to calculate the spoke length. I would like to know what do I need to consider in the calculation for the nipple eyelets not being EXACTlY in the center of the rim. They are offset by a little on every other eyelet. Looks like left and right spokes. Please advise. Thanks in advance!. I am planning on installing DT Swiss DB spokes with DT Red anodized Aluminum nipples. I will probably still go with radial spoking on the front and 3x on both sides of the rear.

You use your ERD sticks and measure at 4 different spots and average the reading. I don't even bother doing that anymore. On good rims one measurement is sufficient.

Always. Measure. Your. ****.

Conversely, you could google the ERD, and find that Sun has it listed on their website.
You take the ERD number, go to king's website and get the hub wheel building specs, and plug all of those into DT's wheelbuilding calculator, which again, you can find via Google. I would highly recommend not using aluminum nipples for a first wheel build, they are unforgiving of uncertain wheelbuilders. Get a lighter rim strip and stick to brass nipples.
The offset does indeed indicate left and right side spoke holes.

I would read sheldon brown's brief and excellent online wheel building tutorial. Again.... Google....

+1 Sheldon's online tutorial is outstanding. I have used it several times.

Do I need to deduct or add for the offset of the nipple eyelets? I will stick to brass nipples, I found some black ones on ebay.. If I had the ERD, 548 (per the rim), would I need that offset measurement? That offset is NOT the OSB right? Thanks again guys..

those rims have quite minor offset and most calculators would churn out the same number for spoke length if you plugged that number in or did not.

an interesting and hotly contested issue to think about is the spoke quality itself. peter white @ peterwhitecycles.com has an interesting article on why he doesn't use DT spokes. while this is a one person case study, i have been building, truing and repairing wheels for 12 years on a professional basis and have only ever seen DT spokes fail at the head of the spoke, never wheelsmith.