I’ve heard it pronounced “gram”. There may be a slight aspiration within the vowel of an almost silent “h”, making it slighty two syllables.
I too say gram, like the unit of mass.
Surprised there’s just the 2 options mentioned so far. It’s definitely not “gram” , but certainly not “gray-um” either. The correct answer is “gra-um” (short A as in grass, not long A as in gray) it sounds awfully close to “gram” but with a very slight pause in the middle
Brits might regionally say Gram, but my Southern England raised SO says Gray-em and has never heard Gram as an alternative pronunciation.
Gra um. No H sound, not a real emphatic Y sound. It’s a family name (used as both a first and last name). This is how we pronounce it, YMMV.
Or…as Bootis says.
That’s just silly. I would naturally pronounce it Grayingcestershireham just like it was originally spelt in the elder days. But people took to pronouncing it Grayshireham (“Grayshrm”) then Graysh’m (origin of the cognate name Gresham BTW) then Graym, leading to any of the various modern pronunciations. Eventually, the written spelling followed suit, more-or-less, giving us Graham.
(My ass is my cite.) 
and you do it a disservice
Except for Graeme Labrooy <-obscure reference
In the ninth dimension, it’s “Big-boo-TAY.”
Other way round: it would never be Gram in the UK. New Zealand, maybe, but that’s not the UK.
I (Midland / Southern English) concur with Eliahna and SciFiSam – I’ve never to the best of my recollection, heard any fellow-Brit say anything but “Gray-em”. (Re Kiwis, I wouldn’t know.)
It’s two syllables in this other ex-British colony. Gray-im for me, but gray-him for others I know.
As it’s my brother’s name I can confidently say it is…Grame, pretty much all one syllable, perhaps the slightest hint of a second syllable as in Grayam but said so quickly that you’ll not notice.
And this is the typical north-east pronunciation in the UK. I have heard a more drawling pronunciation with two definitely separate syllables in other parts of the UK but I’ve certainly never heard “Gram”.
Same as “gram.” But it’s one of the few words (word pairs, in this case) which, when pronounced exactly as I do, could be regarded as having either one syllable or two. This is simply a consequence of the mouth transitioning from the “broad a” sound (the “ae” ligature in IPA notation) to the “m” sound. The mouth is forced to move in a way which creates a little schwa sound right before the “m.” It’s up to the listener to decide if that fleeting “uh” deserves its own syllable or not.
Another “gram” over here.
Gray-im in Ireland. When I hear an American say “Gram Greene” it grinds my gears.
Two syllables generally for me. Unless told otherwise, I say “gray-um.” I say it the same way in “graham cracker.” I’m born & raised in the US. For all I know, this might just be a personal quirk. I also pronounced words like “Tube” and “Tuesday” with a “soft T” (something like “ch,” but more properly a “t[sub]y[/sub]” when I was a kid, and I have no idea where I could have gotten that from, as I had no British English influence growing up that I am consciously aware of.) That one shifted to the usual American pronunciation by the time I was a few grades into elementary school.
Gram. Exactly like the unit of mass. Ditto for the crackers.
I pronounce the crackers “gray-um” but the name “gram”. Go figure!
But the “gray” is not quite like the color. The “a” is softer, but not like the “a” in “at”. About inbetween the two pronunciations.