Volume Calculator

Mold Box Volume - Rectangular

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Part Volume

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Net Volume

Box Volume (in.³)
–  Part Volume (in.³)
=  Net Volume (in.³)

Mold Box Volume - Cylindrical

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Part Volume

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Net Volume

  Cylinder Volume (in.³)
- Part Volume (in.³)
= Net Volume (in.³)

Amount of RTV Needed for Making a Silicone Rubber Mold

Note: There are 21 grams per cubic inch of Silicone Rubber.

There are 453 grams in 1lb.

Formula for a Square/Rectangle Mold: Length x Width x Height

Example: You have a mold box that needs to be filled up 9" x 4" x 2" = 72 cubic inches in order to completly cover your original/part.

Now using the same formula subtract the cubic inches (volume) of your part.

Example: Your part is 8" x 3.5" x 1.5" = 42 cubic inches.

Then you would take 72 - 42 to give you a total of 30 cubic inches.

30 cubic inches x 21 grams per cubic inch = 630 grams of RTV needed.

And then if you want to calculate that into lbs. take 630 divided by 453 grams per lb. = 1.39 lbs. of RTV.

Formula for a Round Mold: Pi x Radius (squared) x Height

Example: The diameter of a mold is 4" (the radius would then be half of that being 2") and the height is 3".

So this is what it would look like:

2" x 2" (radius squared) x 3.14 (pi) x 3 (height) = 37.68 cubic inches.

Now using the same formula subtract the cubic inches of your part.

Example: The part is 3.5" diameter (1.75" radius) by 2.75" high.

So this is what it would look like:

1.75" x 1.75" (radius squared) x 3.14 (pi) x 2.75" (height) = 26.45 cubic inches.

Then you would take 37.68 - 26.45 to give you a total of 11.23 cubic inches.

11.23 cubic inches x 21 grams per cubic inch = 236 grams of RTV needed.

And then if you want to calculate that into lbs. take 236 divided by 453 grams per lb. = .52 lbs. of RTV.

Amount of Resin Needed to Cast a Part

Note: There is .554 ounces in 1 cubic inch of Alumilite Resin.

Formula for a Square/Rectangular Piece: Length x Width x Height

Example: If your piece is 3" x 4" x 2" = 24 cubic inches. Take 24 cubic inches x .554 ounces per cubic inch = 13.25 ounces.

Formula for a Round Piece: Pi x Radius (squared) x Height.

Use the same formula as the RTV round mold (section 1) to calculate resin needed. Then multiply that by .554 ounces per cubic inch to determine ounces needed.