I recall the question of "what is a dram" some time ago on this forum... and as it has resurfaced here it prompted me to dig out a measuring cup I received - correct or not - that shows many different increments - and equates drams to fl. ozs. as:
1 dram = 1/8 fluid ounce
2 drams = 1/4 fluid ounce..... right up to 8 drams = 1 fluid ounce.
Then - to clarify if this was referrring to U.S fluid ounces or UK fluid ounces I revisited a website handy for such conversions to confirm - and it seems to agree - that 8 drams = 1 fluid ounce (U.S. liquid).
http://www.onlineconversion.com/volume.htm
According to Webster's Dictionary - a dram is
1. "a unit of apothecaries' weight equal to 3.89 grams or
2. "a unit of avoirdupois weight eaual to 1.77 grams (and with the concentration of French ownership - we may see this gain in recognition

)... or
3. "a small drink of alcoholic liquor" ... Oh, where is Mr. Picky when we need him???
Otherwise - I understand that "dram" has been colloquialized to mean:
a drink amongst friends, and I'd agree with Lambda:
Or you can just pour whatever that looks nice
Cheers, Dave.