On this page you'll find the exact dimensions for the GMC Sierra Extended Cab 1500 generation 3, made from 2007 to . Below we'll list the dimensions for this pickup from verified sources. First, let's make sure you have the right dimensions in front of you:

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Dimensions in tables

Sierra truck bed dimensions (Extended Cab)

Truck bed dimensions	Short Box (5.75')	Standard Box (6.5')	Long Box (8')
Volume (cu. ft.)	49.6	56.9	73.9
Length at floor	69.2	78.7	97.6
Inside height	19.5	19.5	19.5
Width at wheelhouse	50	50	50
Maximum width at floor	60.2	64.8	64.8

Wheelbase of the Sierra:

Wheelbase	Length (inch)
Short Box (5.75')	134
Standard Box (6.5')	143.5
Long Box (8')	157.5

Exterior dimensions of the Sierra Extended Cab:

Dimension	4x2	4x4
Overall length - Short Box (5.75')	217.9	217.9
Overall length - Standard Box (6.5')	227.4	227.4
Overall length - Long Box (8')	246.6	246.6
Height - Short Box (5.75')	71.2	71.2
Height - Standard Box (6.5')	71.2	71.2
Height - Long Box (8')	70.8	70.8

Exterior width of the Extended Cab:

Exterior width	4x2	4x4
Overall width - Short Box (5.75')	78.5	78.5
Overall width - Standard Box (6.5')	78.5	78.5
Overall width - Long Box (8')	78.5	78.5
Width (mirrors folded)	81.5	81.5
Width (mirrors extended)	93.1	93.1

Extended Cab miscellaneous dimensions

Miscellaneous dimensions	4x2	4x4
Min. ground clearance - Short Box (5.75')	8	8.7
Min. ground clearance - Standard Box (6.5')	8	8.7
Min. ground clearance - Long Box (8')	8	8.4
Ground to top of load floor - Short Box (5.75')	31.6	33.7
Ground to top of load floor - Standard Box (6.5')	31.6	33.7
Ground to top of load floor - Long Box (8')	31.6	33.7

Interior dimensions

1st row dimensions	Extended Cab
Head room	41
Shoulder room	61.4
Hip room	63.9
Leg room	41.3
2nd row dimensions	Extended Cab
Head room	38.4
Shoulder room	65.1
Hip room	61.4
Leg room	33.7