Biparietal diameter (BPD) is the diameter across the developing baby's skull, from one parietal bone to the other. The measurement is useful in dating the pregnancy and estimating fetal weight after about 13 weeks of pregnancy.

Mercury's diameter (at the equator) = 48,800,000cmVenus' diameter = 121,040,000cmEarth's diameter = 127,560,000cmMars' diameter = 67,940,000cmJupiter's diameter = 1,429,840,000cmSaturn's diameter = 1,205,340,000cmUranus' diameter = 511,140,000cmNeptune's diameter = 495,320,000cm

If you mean the diameter of a circle with area pi, then the diameter is 2.

If you mean the diameter of a circle with circumference pi, then the diameter is 2.

If you mean the diameter of a circle with diameter pi, then the diameter is pi.

If you mean the diameter of a circle with radius pi, then the diameter is 2pi.

nominal diameter is the original diameter of an object

the inner diameter is the shaft diameter

the out diameter you have to calculated