Calculators vary as to the assumptions that they make.

If you used a good one and its assumptions match the measurement method of your spoke manufacturer, you will most likely be unable to tension the front wheel with 264's and possibly even 262's (spokes will be undertensioned even when screwed all the way into nipples), and you'll have rear left spokes engaged with the nipples barely halfway if you use 260's there.

Your typical nipple has 9 mm of thread and you want to engage as much of that as possible without going over.