Although the time varies with the type of duck, the eggs of most common ducks hatch in 28 days. Commercial egg farmers typically keep eggs in incubators for 25 days. Eggs are often in hatchers for the final three days.
Incubators for duck eggs are typically kept at 99.5 degrees Fahrenheit, with a relative humidity level of 55 percent. The incubating device turns the eggs several times daily. A few days before hatching, the eggs are placed in hatchers set at a constant temperature of 99 degrees Fahrenheit. The humidity starts off at 65 percent, but when the ducklings begin to break through, that level is raised to 80 percent. Temperature and humidity are lowered slightly at the end of the process.