Measure the triangle - BB>Saddle, Saddle>Bars, Bars>BB. I've done this to all my bikes now rotating forward/backward depending on what the bike is used for. The Bars on the TT bike are about 2-3" lower than my track bike so the saddle has been pushed forward to fit. It's still comfortable for the distance I ride it. The road and mountain bike are more relaxed so the triangle has been rotated backwards.
If you have different saddles on each bike there's no point measuring from the tip as saddles are of different shapes and sizes. Measure from the point were you sit.
Measure the triangle - BB>Saddle, Saddle>Bars, Bars>BB. I've done this to all my bikes now rotating forward/backward depending on what the bike is used for. The Bars on the TT bike are about 2-3" lower than my track bike so the saddle has been pushed forward to fit. It's still comfortable for the distance I ride it. The road and mountain bike are more relaxed so the triangle has been rotated backwards.
If you have different saddles on each bike there's no point measuring from the tip as saddles are of different shapes and sizes. Measure from the point were you sit.