Unit and Building (gap) sizes in pixels

1-Use a regular mapmaker (without stacking, snapping buildings to the grid) to plot down all sorts of buildings you want to analyze, in any type of map, doesn't matter because you're not going to play in it.
2-Save, close, and open up that map on "Starcraft X-tra Editor", classic mode. Set it to show the matrix grid.
This editor shows the true "physical" boundaries for every building and unit as you are placing them, but at the same time it doesn't feature the ability of placing buildings aligned to the grid, so that's why step 1 is necessary..
3- Select a building from the palette, hover over the building in the map, make sure it's exactly on top, and take a screenshot. (print screen)
4- Open up the screenshot with whatever image program you want, even mspaint is good enough for this. Ctrl+v, zoom up, and count how many pixels the building boundary is away from the grid, on each side. Using the select tool helps also. (...)
5- Repeat from 3, selecting another building, and another, and another, until you're done.
5- This is easier to do with units since you don't have to align nothing at all and you only need to hover it around and screenshot. Measuring just the dimensions is faster as well.

Of course this is extremely inefficient, a better way would be to take that info directly from the starcraft MPQ or wherever the unit and building sizes may be, but time is something I have plenty so why not do it the painful and repetitive way? (I didn't even check the MPQs before devoting hours into this...)

There is only one concern with this procedure - I'm not even sure if this SC X-tra editor even draws the unit sizes from the MPQ, because the forge boundaries were screwed up (it was taking like 10x2 matrices) and I had to download a patch to fix it. So if it turns out this editor is taking these values from elsewhere then this is only as accurate as whoever set these values in the editor wanted them to be... which may be real bad or just perfect, I don't know. Didn't verify enough myself just yet.
"Source" material:
+ Show Spoiler +

# unitsizes.py - Starcraft building and unit sizes parser

def unit_output (name, left_gap, right_gap, top_gap, bottom_gap,
box_width, box_height, real_width, real_height,
dimensions0,dimensions1,dimensions2,dimensions3):
#idented_name= name
#while len(idented_name)<30 :
# idented_name = "_" + idented_name
#output = '%s: %s,%s,%s,%s (%sx%s)' % (idented_name, left_gap, right_gap, top_gap, bottom_gap, width, height)
#output = "{0:>30}: {3:>3},{1:>3},{2:>3},{4:>3} ({5:>1}x{6})".format(name,left_gap,right_gap,top_gap,bottom_gap,width,height)
#remove underline imo... w/e
output="{0:_>30}: {3:>3},{1:>3},{2:>3},{4:>3} ({5:>3}x{6:<3}) ({7:>3}x{8:<3})"\
.format(name,left_gap,right_gap,top_gap,bottom_gap,box_width,
box_height,real_width,real_height)
outputd= ' %s %s %s %s' % (dimensions0,dimensions1,dimensions2,dimensions3)
#output = output + outputd
return output

units_database = [
#['',[,,,],None,[,]],
['Terran Marine',[8,8,9,10],None,[20,17]],
['Terran Ghost',[7,7,10,11],None,[22,15]],
['Terran Vulture',[16,15,16,15],None,[32,32]],
['Terran Goliath',[16,15,16,15],None,[32,32]],
['Terran Siege Tank (Tank Mode)',[16,15,16,15],None,[32,32]],
['Terran Scv',[11,11,11,11],None,[23,23]],
['Terran Wraith',[19,18,15,14],None,[30,38]],
['Terran Science Vessel',[32,32,33,16],None,[50,65]],
['Terran Dropship',[24,24,16,20],None,[37,49]],
['Terran Battlecruiser',[37,37,29,29],None,[64,80]],
['Spider Mine',[7,7,7,7],None,[16,16]],
['Nuclear Missle',[7,7,14,14],None,[32,32]],
['Terran Civilian',[8,8,9,10],None,[20,17]],
['Terran Siege Tank (Siege Mode)',[16,15,16,15],None,[32,32]],
['Terran Firebat',[11,11,7,14],None,[28,23]],
['Scanner Sweep',[13,13,13,17],None,[31,27]],
['Terran Medic',[8,8,9,10],None,[20,17]],
['Zerg Larva',[8,7,8,7],None,[16,16]],
['Zerg Egg',[16,15,16,15],None,[32,32]],
['Zerg Zergling',[8,7,4,11],None,[16,16]],
['Zerg Hydralisk',[10,10,10,12],None,[23,21]],
['Zerg Ultralisk',[19,18,16,15],None,[32,38]],
['Zerg Broodling',[9,9,9,9],None,[19,19]],
['Zerg Drone',[11,11,11,11],None,[23,23]],
['Zerg Overlord',[25,24,25,24],None,[50,50]],
['Zerg Mutalisk',[22,21,22,21],None,[44,44]],
['Zerg Guardian',[22,21,22,21],None,[44,44]],
['Zerg Queen',[24,23,24,23],None,[48,48]],
['Zerg Defiler',[13,13,12,12],None,[25,27]],
['Zerg Scourge',[12,11,12,11],None,[24,24]],
['Infested Terran',[8,8,9,10],None,[20,17]],
['Infested Kerrigan',[7,7,10,11],None,[22,15]],
['Terran Valkyrie',[24,24,16,20],None,[50,50]],
['Mutalisk Cocoon',[16,15,16,15],None,[32,32]],
['Protoss Corsair',[18,17,16,15],None,[32,36]],
['Protoss Dark Templar (Unit)',[12,11,6,19],None,[30,24]],
['Zerg Devourer',[22,21,22,21],None,[44,44]],
['Protoss Dark Archon',[16,15,16,15],None,[32,32]],
['Protoss Probe',[11,11,11,11],None,[23,23]],
['Protoss Zealot',[11,11,5,13],None,[27,23]],
['Protoss Dragoon',[15,16,15,16],None,[32,32]],
['Protoss High Templar',[12,11,10,13],None,[28,24]],
['Protoss Archon',[16,15,16,15],None,[32,32]],
['Protoss Shuttle',[20,19,16,15],None,[32,40]],
['Protoss Scout',[18,17,16,15],None,[32,36]],
['Protoss Arbiter',[22,21,22,21],None,[44,44]],
['Protoss Carrier',[32,31,32,31],None,[64,64]],
['Protoss Interceptor',[8,7,8,7],None,[16,16]],
['Protoss Reaver',[16,15,16,15],None,[32,32]],
['Protoss Observer',[16,15,16,15],None,[32,32]],
['Protoss Scarab',[2,2,2,2],None,[5,5]],

['Rhynadon (Badlands Critter)',[16,15,16,15],None,[32,32]],
['Bengalaas (Jungle Critter)',[16,15,16,15],None,[32,32]],
['Scantid (Desert Critter)',[16,15,16,15],None,[32,32]],
['Kakaru (Twilight Critter)',[16,15,16,15],None,[32,32]],
['Ragnasaur (Ashworld Critter)',[16,15,16,15],None,[32,32]],
['Ursadon (Ice World Critter)',[16,15,16,15],None,[32,32]],

['Lurker Egg',[15,16,15,16],None,[32,32]],
['Map Revealer',[13,13,13,17],None,[31,27]],

['Zerg Lurker',[15,16,15,16],None,[32,32]],
['Disruption Web',[60,59,40,39],None,[100,140]],

['Terran Command Center',[58, 58, 41, 41],None,[96, 128]],
['Terran Comsat Station',[37,31,16,25],[128,32],[64,64]],
['Terran Nuclear Silo',[37,31,16,25],[128,32],[64,64]],
['Terran Supply Depot',[38,38,22,26],None,[64,96]],
['Terran Refinery',[56,56,32,31],None,[64,128]],
['Terran Barracks',[48,56,40,32],None,[96,128]],
['Terran Academy',[40,44,32,24],None,[64,96]],
['Terran Factory',[56,56,40,40],None,[96,128]],
['Terran Starport',[48,48,40,38],None,[96,128]],
['Terran Control Tower',[47,28,24,22],[128,32],[64,64]],
['Terran Science Facility',[48,48,38,38],None,[96,128]],
['Terran Covert Ops',[47,28,24,22],[128,32],[64,64]],
['Terran Physics Lab',[47,28,24,22],[128,32],[64,64]],
['Terran Machine Shop',[39,31,24,24],[128,32],[64,64]],
['Terran Engineering Bay',[48,48,32,28],None,[96,128]],
['Terran Armory',[48,47,32,22],None,[64,96]],
['Terran Missle Turret',[16,16,32,16],None,[64,64]],
['Terran Bunker',[32,32,24,16],None,[64,96]],

['Norad II (Crashed)',[48,47,32,31],None,[64,96]],
['Ion Cannon',[48,47,32,31],None,[64,96]],
['Uraj Crystal',[16,15,16,15],[0,0],[32,32]],
['Khalis Crystal',[16,15,16,15],None,[32,32]],

['Infested Command Center',[58,58,41,41],None,[96,128]],
['Zerg Hatchery',[49,49,32,32],None,[96,128]],
['Zerg Lair',[49,49,32,32],None,[96,128]],
['Zerg Hive',[49,49,32,32],None,[96,128]],
['Zerg Nydus Canal',[32,31,32,31],None,[64,64]],
['Zerg Hydralisk Den',[40,40,32,24],None,[64,96]],
['Zerg Defiler Mound',[48,48,32,4],None,[64,128]],
['Zerg Greater Spire',[28,28,32,24],None,[64,64]],
['Zerg Queen\'s Nest',[38,32,28,28],None,[64,96]],
['Zerg Evolution Chamber',[44,32,32,20],None,[64,96]],
['Zerg Ultralisk Cavern',[40,32,32,31],None,[64,96]],
['Zerg Spire',[28,28,32,24],None,[64,64]],
['Zerg Spawning Pool',[36,40,28,18],None,[64,96]],
['Zerg Creep Colony',[24,23,24,23],None,[64,64]],
['Zerg Spore Colony',[24,23,24,23],None,[64,64]],
['Zerg Sunken Colony',[24,23,24,23],None,[64,64]],
['Zerg Overmind (With Shell)',[80,79,32,40],None,[96,160]],
['Zerg Overmind',[80,79,32,40],None,[96,160]],
['Zerg Extractor',[64,63,32,31],None,[64,128]],

['Mature Chrysalis',[32,31,32,31],None,[64,64]],
['Zerg Cerebrate',[40,32,32,31],None,[64,96]],
['Zerg Cerebrate Daggoth',[40,32,32,31],None,[64,96]],

['Protoss Nexus',[56,56,39,39],None,[96,128]],
['Protoss Robotics Facility',[36,40,16,20],None,[64,96]],
['Protoss Pylon',[16,16,12,20],None,[64,64]],
['Protoss Assimilator',[48,48,32,24],None,[64,128]],
['Protoss Observatory',[44,44,16,28],None,[64,96]],
['Protoss Gateway',[48,48,32,40],None,[96,128]],
['Protoss Photon Cannon',[20,20,16,16],None,[64,64]],
['Protoss Citadel of Adun',[24,40,24,24],None,[64,96]],
['Protoss Cybernetics Core',[40,40,24,24],None,[64,96]],
['Protoss Templar Archives',[32,32,24,24],None,[64,96]],
['Protoss Forge',[36,36,24,20],None,[64,96]],
['Protoss Stargate',[48,48,40,32],None,[96,128]],
['Stasis Cell/Prison',[64,63,48,47],None,[96,128]],
['Protoss Fleet Beacon',[40,47,32,24],None,[64,96]],
['Protoss Arbiter Tribunal',[44,44,28,28],None,[64,96]],
['Protoss Robotics Support Bay',[32,32,32,20],None,[64,96]],
['Protoss Shield Battery',[32,32,16,16],None,[64,96]],

['Khaydarin Crystal Formation',[64,63,48,47],None,[96,128]],
['Protoss Temple',[112,111,48,47],None,[96,224]],
['Xel`Naga Temple',[80,79,34,63],None,[128,160]],
['Mineral Field (Type 1)',[32,31,16,15],None,[32,64]],
['Mineral Field (Type 2)',[32,31,16,15],None,[32,64]],
['Mineral Field (Type 3)',[32,31,16,15],None,[32,64]],
['Vespene Geyser',[64,63,32,31],None,[64,128]],
['Warp Gate',[48,47,32,31],None,[64,96]],
['Psi Disrupter',[80,69,38,47],None,[96,160]],
['Zerg Beacon',[48,47,32,31],None,[64,96]],
['Terran Beacon',[48,47,32,31],None,[64,96]],
['Protoss Beacon',[48,47,32,31],None,[64,96]],
['Zerg Flag Beacon',[48,47,32,31],None,[64,96]],
['Terran Flag Beacon',[48,47,32,31],None,[64,96]],
['Protoss Flag Beacon',[48,47,32,31],None,[64,96]],
['Power Generator',[56,63,28,43],None,[96,128]],
['Overmind Cocoon',[48,47,32,31],None,[64,96]],
['Dark Swarm',[80,79,80,79],None,[160,160]],

['Floor Missle Trap',[32,31,32,31],None,[64,64]],
['Left Upper Level Door',[25,44,17,20],None,[136,136]],
['Right Upper Level Door',[44,25,17,20],None,[136,136]],
['Left Pit Door',[41,28,17,20],None,[100,148]],
['Right Pit Door',[28,41,17,20],None,[100,148]],
['Floor Gun Trap',[32,31,32,31],None,[64,64]],
['Left Wall Missle Trap',[16,15,16,15],None,[64,64]],
['Left Wall Flame Trap',[16,15,16,15],None,[64,64]],
['Right Wall Missle Trap',[16,15,16,15],None,[64,64]],
['Right Wall Flame Trap',[16,15,16,15],None,[64,64]],
['Start Location',[48,48,32,32],None,[96,128]],
['Flag',[16,15,16,15],None,[32,32]],
['Young Chrysalis',[16,15,16,15],None,[32,32]],
['Psi Emitter',[16,15,16,15],None,[32,32]],
['Data Disc',[16,15,16,15],None,[32,32]],
['Khaydarin Crystal',[16,15,16,15],None,[32,32]],
['Mineral Cluster Type 1',[16,15,16,15],None,[32,32]],
['Mineral Cluster Type 2',[16,15,16,15],None,[32,32]],
['Protoss Vespene Gas Orb Type 1',[16,15,16,15],None,[32,32]],
['Protoss Vespene Gas Orb Type 2',[16,15,16,15],None,[32,32]],
['Zerg Vespene Gas Sac Type 1',[16,15,16,15],None,[32,32]],
['Zerg Vespene Gas Sac Type 2',[16,15,16,15],None,[32,32]],
['Terran Vespene Gas Tank Type 1',[16,15,16,15],None,[32,32]],
['Terran Vespene Gas Tank Type 2',[16,15,16,15],None,[32,32]],

#['',[,,,],None,[,]],
]

#heading
print "{0:=^31} top, <-, ->,bottom (box) (real size)".format('Unit Gaps and Dimensions')

for unit in units_database:
unit_name = unit[0]

box_data = unit[3]
box_height = box_data[0]
box_width = box_data[1]

#matrix_width = box_width/32
#matrix_height = box_height/32

dimensions = unit[1]

# +1x1 right/bottom pixel center fix,
dimensions[1] += 1
dimensions[3] += 1

#Gaps, w\ noob rounding fix, worst way possible
#these are odds
if box_width%2==1:
left_gap = box_width/2 - dimensions[0]
right_gap = box_width/2 +1 - dimensions[1]
if box_height%2==1:
top_gap = box_height/2 - dimensions[2]
bottom_gap = box_height/2 +1 - dimensions[3]
#these.. arent
if box_width%2==0:
left_gap = box_width/2 - dimensions[0]
right_gap = box_width/2 - dimensions[1]
if box_height%2==0:
top_gap = box_height/2 - dimensions[2]
bottom_gap = box_height/2 - dimensions[3]

#shifting fix
#I could just leave it but meh
if top_gap == -bottom_gap:
top_gap,bottom_gap = 0,0
if left_gap == -right_gap:
left_gap,right_gap = 0,0

real_width = dimensions[0] + dimensions[1]
real_height= dimensions[2] + dimensions[3]

print unit_output(unit_name, left_gap, right_gap, top_gap, bottom_gap,
box_width, box_height, real_width, real_height,
dimensions[0],dimensions[1],dimensions[2],dimensions[3],)

I've only measured the space missing from a full matrix grid
Remember one matrix, 1x1, is 32 pixels wide and 32 pixels high, or 32x32 (px)

So for example, a supply depot which is built in an area of (32*3)x(32*2) or 96x64 (px)
But that doesn't really matter much. What we really want to know are the size of the gaps.
The supply got a gap of 6 pixels at the top, 10 pixels to the left, 9 to the right, and 5 pixels below.

The format of this list is:
name top left right bottom matrices

sunken 8 8 8 8 2x2
spore 8 8 8 8 2x2
creep 8 8 8 8 2x2
hatch 16 15 14 15 4x3
lair 16 15 14 15 4x3
hive 16 15 14 15 4x3
extractor 0 0 0 0 4x2
pool 4 12 7 13 3x2
spire 0 4 3 7 2x2
g. spire 0 4 3 7 2x2
ultra m. 0 8 15 0 3x2
evoc. 0 4 15 11 3x2
queens n. 4 10 15 3 3x2
defilerm. 0 16 15 27 4x2
hydra d. 0 8 7 7 3x2
nydus c. 0 0 0 0 2x2
infest cc 7 6 5 6 4x3

shield b. 16 16 15 15 3x2
pylon 20 15 16 11 2x2
observat. 16 4 3 3 3x2
cannon 16 12 11 15 2x2
nexus 9 8 7 8 4x3
gateway 16 16 15 7 4x3
cyber c. 8 8 7 7 3x2
fleet b. 0 8 0 7 3x2
stargate 8 16 15 15 4x3
citadel 8 24 7 7 3x2
templr a. 8 16 15 7 3x2
forge 8 12 11 11 3x2
assimila. 0 16 15 7 4x2
arbitr t. 4 4 3 3 3x2
robo faci 16 12 7 11 3x2
robo supb 0 16 15 11 3x2

supply d. 10 10 9 5 3x2
starport 8 16 15 9 4x3
sci. fcl. 10 16 15 9 4x3
refinery 0 8 7 0 4x2
turret 0 16 15 15 2x2
factory 8 8 7 7 4x3
eng. bay 16 16 15 19 4x3
CC 7 6 5 6 4x3
bunker 8 16 15 15 3x2
armory 0 0 0 9 3x2
barracks 8 16 7 15 4x3
academy 0 8 3 7 3x2

========================
Units
zealot 23x19
probe 23x23
high t. 24x24
dark t. 24x26

reaver 32x32
archon 32x32
dark arch 32x32
dragoon 32x32
------------------
zergling 16x16
infested 17x20
broodling 19x19
hydralisk 21x23
drone 23x23
defiler 27x25

lurker 32x32
ultralisk 38x32
-----------------
ghost 15x22
medic 17x20
marine 17x20
firebat 23x22
scv 23x23

tank 32x32
tank sg'd 32x32
goliath 32x32
vulture 32x32
---------------------
dark swarm 160x160
disruption web 120x80

---------------
air units (...)

observer 32x32
scout 36x32
corsair 36x32
shuttle 40x32
arbiter 44x44
carrier 64x64

scourge 24x24
mutalisk 44x44
guardian 44x44
devourer 44x44
queen 48x48
overlord 50x50

wraith 38x30
valkyrie 49x37
dropship 49x37
scivessel 65x50
battle c. 75x59