Charles, I have lots of 2.8, 3, 5 and 6.5 gallon carboys. Each size varies
in the volume of liquid they hold but it's not a big difference. Long ago I
calibrated each size by adding water in increments and measuring the height
of the water with a yard stick. These measurements have served me well and
allow for selection of a receiving carboy when racking or blending. Send me
an email address and I'll send you my chart.

Bill Frazier
Olathe, Kansas USA

Sedgewick Halbritton wrote " I always end up guessing when blending
> from multiple carboys into a single carboy. It would also be nice to
> know exactly how much wine is in the carboy for more accurate chemical
> additions. Any ideas???