Is width measured horizontally and depth/length measured vertically?

Formula For Average Gallons In Rectangle, Square Or Freeform Pools:
Length x Width x Average Depth x 7.5 = Total gallons
Formula For Average Gallons In Circular Pools:
Diameter x Diameter x Average Depth x 5.9 = Total gallons
Formula For Average Gallons In Oval Pools:
Length x Width x Average Depth x 5.9 = Total gallons
Formula For Average Depth Of Pools With Slopes:
Shallow End Depth + Deep End Depth Divided by 2 = Average Depth

volume = length*width*depth
V=5000*3000*100
V=1500000000 mm^3
or
V=1.5 m^3

thats 6 meters square need another factor[HEIGHT ] for cube 12x .5x ?=CUBIC

Use a Tape Measure:
Measure the Length, Width & Depth of the inside or outside and use this to calculate the cubic feet or meters.

It's a rectangle, so it's far easier than a circle.

http://www.autocalculator.org/Calculators/Cubic-feet-formula.aspx#.VsvxQzY0nXE

Calculator
Cubic Feet Calculator

What you looking to know?

Square feet suggests a flat area, like the floor plan of the pool, which would be 16 x 32 = 512 square feet. Like you'd measure walls for tiles or paper etc.

As you've given 3 dimensions, sounds like your after the cubic capacity/volume of the pool, in which case your looking at cubic feet (same as flat area above, but with the added depth to go from flat 2d, to 3d (2 vs 3 dimensions)), which would be 16 x 32 x 10 = 5,120 cubic feet.

not possible to calculate with the information provided. here is a basic formula to get you close.
length x width x average depth x height in feet x 7.5 gallons / cubic ft

Measure the width, depth, and height in inches of the interior cavity.

Multiply the length by the width by the height to get the total in cubic inches.

Divide the cubic inches by 1,728.

The resulting number will be your microwave's capacity in cubic feet.

What you appear to be asking is the volume of your Pool in gallons! Here is the formula and resulting answer:

Length X Width X average Depth X 7.5 (for rectangluar) (or 5.9 for a circle or oval)

You need to know 3 values:

The overall length in feet (assuming 42 on your note)
The overall Width in feet (assuming 16 on your note)
The average depth, take a depth measurement at 3-4 locations equally apart along the length from deep to shallow (or vice-versa) (example might 8ft, 6ft, 4ft, 3ft) add these measurements together and then divide the total sum by the number of depth measurements (example 4) this will be the average (example 5.25)

So the resulting formula would read 42 x 16 x 5.25 x 7.5 = 26,460 gallons for the example

So if your pool's average depth is about the same, then your volume is rounded to about 26,500

Your shock product should clearly state how much one bag will treat a given volume (example 10,000 gals) for regular treatment or shocking. Usually shocking involves doubling or even tripling the normal maintenance dosage, but check the product labels and instructions for manufacturer's recommendation.

A frame has 4 basic frame sizes.1. Eye Size - refers to the horizontal width in millimeters of one of the frame's lenses.
2.Bridge Size - measurement is the distance in millimeters between the two lenses. It is measured between the two closest points of the two lenses.
3.Temple Size - is measured along the length of the temple, from one end to the other, including the bend.
4.Vertical Size (B) - refers to the vertical height of an eyeglasses lens, and is measured from the tip to the bottom of the lens aperture of the frame. The measurements are taken from a horizontal line intersecting with the top of the lens, to the horizontal line intersecting with the bottom edge of the lens. The B measurement is only important when ordering multifocal lenses; follow this link to read more about progressive lenses.

So whats the question ?