BCF's Animal Foetal Ageing app allows you to calculate the approximate foetal age of cattle, sheep and horses from standard measurements, the following measurements are supported.

Cattle Crown Rump Length (Length from the crown of the skull to the base of the tail)
Cattle Trunk Diameter (Diameter of the abdomen at the umbilicus)
Cattle Head Diameter (Diameter of the skull in the plane of the eye orbits)
Cattle Head Length (Length from poll to muzzle)
Cattle Eye Diameter (Diameter of the eye)

Sheep Trunk Diameter (Diameter of the abdomen at the umbilicus)
Sheep Head Diameter (Diameter of the skull in the plane of the eye orbits)

Horse Equine Conceptus Diameter (Diameter of the conceptus)
Horse Foetal Eye Length (Diameter of the eye)

Enter the measurement in mm, select the measurement type and the app will give you the approximate age in days.

The app can also be used in reverse, enter the age in days, select the measurement type and the app will return the size in mm.

If the measurement is out of range for the selected type, then the range will be displayed in red.

The calculations are based on the best published data available for the given measurements, but they are approximate and will vary between breeds and even between individuals within breeds.