Introduction
While Halo 4’s Forge Objects within the Structure Pallet may be based off Halo: Reach’s alliteration, they are not identical. Differences from Reach to 4 include not only new textures, but many objects have noticeable changes as well. This thread, while it may seem late, will provide Forgers the approximate amount of space (not necessarily volume) that each object covers up.
Hopefully, after reading this, effectively drawing out your maps prior to Forging them will become a hell of a lot easier for you.
ITT, each Forge Object is measured by Blocks (abbriviated as Blc). A block, in game, is ten intervals in the coordinate plane (the size of a Block 1x1). However, it must be noted that not all objects can be measured by a whole number of blocks, but will be represented with decimal places. As an example, a Block 1x1, Flat is 1 bloc long, 1 block wide, and 0.20 blocks tall.
The format for measuring each side of an object is the length (the longest side) times the width (the shorter side) times the height. This will be displayed as the following: L x W x H
And with all of that being said, may the list begin…
Building Blocks:

Block 1x1: 1.0 x 1.0 x 1.0 Block 1x1, Flat: 1.0 x 1.0 x 0.2 Block 1x1, Short: 1.0 x 1.0 x 0.5 Block 1x1, Tall: 1.0 x 1.0 x 3.0 Block 1x1, Tall and Thin: 1.0 x 0.5 x 3.0 Block 1x2: 1.0 x 1.0 x 2.0 Block 1x4: 1 x 1 x 4

Block 2x1, Flat: 2 x 1 x 0.2 Block 2x2: 2 x 2 x 2 Block 2x2, Flat: 2 x 2 x 0.2 Block 2x2, Short: 2 x 2 x 0.5 Block 2x2, Tall: 2 x 2 x 3 Block 2x3: 3 x 2 x 1 Block 2x4: 4 x 2 x 1

Block 3x1, Flat: 3 x 1 x 0.2 Block 3x3: 3 x 3 x 1 Block 3x3, Flat: 3 x 3 x 0.2 Block 3x3, Short: 3 x 3 x 0.5 Block 3x3, Tall: 3 x 3 x 3 Block 3x4: 4 x 3 x 1

Block 4x4: 4 x 4 x 1 Block 4x4, Flat: 4 x 4 x 0.2 Block 4x4, Short: 4 x 4 x 0.5 Block 4x4, Tall: 4 x 4 x 3

Block 5x1 Short (Flat): 5 x 1 x 0.2 Block 5x5, Flat: 5 x 5 x 0.5
Bridges and Platforms:

Bridge, Small: 1 x 2.5 x 0.2 Bridge, Medium: 2 x 2.5 x 0.2 Bridge, Large: 3 x 2.5 x 0.2 Bridge, XLarge: 5 x 2.5 x 0.2

Bridge Diagonal: 5 x 5 x 0.2 Bridge Diagonal, Small: 4 x 4 x 0.2

Dish: 12 x 6 x 3 Dish, Open: 12 x 6 x 3

Corner, 45 Degrees: 2 x 1.2 x 0.2 Corner 2x2: 2 x 2 x 0.2 Corner 4x4: 4.2 x 4.2 x 0.2

Landing Pad: 6 x 5 x 0.2

Platform, Ramped: 5 x 5 x 12 Platform, Large: 4 x 4 x 3 Platform, XL: 4.5 x 4.5 x 4 Cylinder, Large: 6.5 x 6.5 x 4

Y Cross: 4 x 3 x 0.2 Y Cross, Large: 5 x 1 x 1.5

Sniper’s Nest: 5 x 2 x 2 Staircase: 7 x 4 x 2.5
Inclines:

Bank 1x1: 1 x 1 x 1 Bank 1x2: 2 x 1 x 1 Bank 2x1: 2 x 1 x 1 Bank 2x2: 2 x 2 x 1

Ramp 1x2: 2 x 1 x 1 Ramp 1x2, Shallow: 2 x 1 x 0.5 Ramp 2x2: 2 x 2 x 1 Ramp 2x2, Steep: 2 x 2 x 2

Ramp Bridge, Small: 3 x 2.5 x 1.5  Ramp Bridge, Medium: 4 x 2.5 x 3 Ramp Bridge, Large: 5 x 2.5 x 3.5

Ramp, XL (Upper Section): 4 x 2 x 3 Ramp, XL (Lower Section): 4 x 2 x 1 Ramp, XL (Total): 4 x 2 x 4.2 Ramp, Stunt: 4 x 2.2 x 1.5
Doors, Windows, and Walls:

Door: 2.5 x 0.25 x 2 Door, Double: 2.2 x 0.2 x 1

Window: 2 x 0.2 x 1 Window, Double: 2 x 0.25 x 2

Wall: 2 x 0.2 x 2 Wall, Double: 4 x 0.2 x 2 Wall, Corner: 2 x 2 x 1 Wall, Coliseum: 10 x 0.5 x 11.8

Tunnel, Short (Exterior): 4 x 1 x 2 Tunnel, Short (Interior): 2 x 1 x 2 Tunnel, Long (Exterior): 5 x 3 x 2 Tunnel, Long (Interior): 3 x 3 x 2
Decorative:

Antenna, Small: 0.25 x 0.25 x 3.5 Antenna, Satellite: 9.75 x 9.75 x 5

Brace: 3 x 0.5 x 2 Brace, Large: 11 x 2 x 4.5 Brace, Tunnel: 3 x 2.5 x 6

Column: 0.33 x 0.33 x 1

Cover: 2.5 x 0.25 x 1.5 Cover, Crenelation: 2.5 x 0.2 x 1 Cover, Glass: 4 x 2 x 2

Railing, Small: 1 x 0.2 x 0.5 Railing, Medium: 2 x 0.2 x 0.5 Railing, Long: 3 x 0.2 x 0.5

Teleporter Frame: 2 x 1.5 x 1.75 Strut: 1.5 x 1 x 4.33 Large Walkway Cover: 12 x 2.5 x 2.66
Buildings:

Bunker Small: 3 x 2.5 x 1.5 Bunker Small, Covered: 3 x 2.5 x 2 Bunker Box: 6 x 2.66 x 2 Bunker Round: 12 x 7 x 2 Bunker Ramp: 5 x 5 x 3

Pyramid: 15 x 8 x 2 Pyramid (Interior Section): 5 x 3 x 2

Tower, 2 Story: 5 x 4 x 4.5 Tower, 3 Story (Story 1): 5 x 4 x 3 Tower, 3 Story (Story 2): 5 x 4 x 5 Tower, Tall (Story 1): 5 x 4 x 3 Tower, Tall (Total): 5 x 4 x 6.33

Room, Double: 5½ x 5 x 2.66 Room, Triple: 12 x 6 x 3.2

Window, Coliseum: 17.5 x 0.66 x 6

Ramp Circular, Small: 4 x 3 x 1 Ramp Circular, Large: 8 x 4 x 2

Base 1: 8.5 x 7 x 5  Base 2, Left: 6.33 x 6 x 6.5 Base 2, Right: 6.33 x 6 x 6.5

Walkway, Large (Portion 1): 6 x 2.4 x 2 Walkway, Large (Intersection): 2 x 2.4 x 6 Walkway, Large (Portion 2) 6 x 2.5 x 2 Walkway, Large (Total): 14 x 2.5 x 6