The math
Turkey incubation is 28 days. That's it. There's no breed-specific math, no wild-versus-domestic adjustment, no seasonal variation worth coding around. Set the egg, wait 28 days, lockdown 3 days before.
hatch_date = set_date + 28 days
lockdown_date = hatch_date - 3 days
Frequently asked
Is wild turkey incubation really the same as domestic?
Yes. Both are 28 days. Domestic turkeys have been bred for size, growth rate, and white feathering (easier to dress), but the embryonic development clock hasn't shifted. A wild Eastern turkey hen sits her nest for the same 28 days a Broad Breasted hen would, if a Broad Breasted hen could still go broody and walk at the same time.
When should I first candle?
Day 10. Earlier candling on turkey eggs is hard because the shells are thicker and more pigmented than chicken eggs. By day 10 you can clearly see veining against a strong candler. Pull clears and obvious early deaths.
Why are turkey hatch rates lower than chicken hatch rates?
Several reasons. Commercial Broad Breasted turkeys can't naturally breed - they need artificial insemination, which lowers fertility. Turkey eggs are larger and more sensitive to temperature and humidity drift. And the poults themselves are more fragile at hatch. A 60 to 75% hatch rate is normal even with good incubator practice.
Can I hatch turkey eggs under a chicken hen?
Yes, with caveats. A broody chicken hen will gladly sit turkey eggs for 28 days. The complication is that turkey poults imprint on the hen and learn her behavior. Raised by a chicken, they tend to flock with chickens for life, which causes feeding and roosting problems later. Most breeders prefer incubator or turkey-hen hatches for that reason.