How long will it take cockateil eggs to hatch?

18-21 days after the start of incubation.

"Cockatiels in captivity generally lay between 3 and 8 eggs per clutch with the average being around 4 to 5 per clutch. The incubation period starts when the hen or pair start sitting on the eggs constantly. Some hens may wait until the 3rd egg to begin the incubation process, so all eggs will hatch close to the same time. Generally though, the hen will start incubating the eggs by the time she lays the 2nd egg. The normal incubation period for cockatiel eggs is between 18 and 21 days (from the day the hen or pair start sitting the eggs). The male and female generally take turns sitting on the eggs and do this in shifts. Some pairs will divide the eggs and each sit on half of them. They will also share the responsibility for feeding the chicks. Eggs will generally hatch every other day. From my observations, the eggs generally hatch in the early morning hours." http://www.birdsnways.com/wisdom/ww22eiv.htm

Usually around 21 days after the laying day is the hatching time for the eggs.