Calculating/Capacity of Soap Molds

If you recently purchased a soap mold and you do not know how much soap base you need to use here are some calculations and formulas to help you out.

Capacity of Shape Molds

Mini Rectangle (1 1/2" x 1" x 1" deep) = 2 oz
Small Rectangle (2 3/4" x 2" x 1" deep) = 3 oz
Medium Rectangle (3 1/4" x 2 1/4 " x 1" deep) = 4 oz
Medium Square (3" x 3" x 1" deep) = 5 oz
Large Square (3" x 6" x 1" deep) = 9 oz
Medium Circle (2 1/2" diameter x 1" deep) = 2 1/2 oz
Domed Small Circle (2 1/2" diameter x 3/4" deep) = 2 oz
Domed Medium Circle (3" diameter x 1" deep) = 4 oz
Medium Oval (2" x 3" x 3/4" deep) = 2 1/2 oz
Domed Medium Oval (2 3/4" x 2 1/2" x 1 1/4" deep) = 4 oz

Capacity of Loaf Molds

Small Loaf Molds (3 1/4" x 4 3/4" x 2 1/2" deep food storage container) = 16 oz to fill
Medium Loaf Molds (4" x 6" x 2 3/4" deep food storage container) = 24 oz to fill

Capacity of Tube Molds
This chart lists how much soap is needed to fill 1" of a tube mold. Use it to calculate how much soap base you need for the number of bars you wish to make. My estimates are for 1" thick bars for molds 2 1/2" in diameter or larger and 1/2" thick bars for smaller tubes.

Plastic molds made for soap are 6" high; metal tube molds are 9" high. Plastic and metal candle molds range from 4" to 10" in height. The tube mold measurements are across the top of the mold and include the width of the mold material.

1" (small) circle - 1/2 oz per 1"
2" (medium) circle - 1 1/2 oz per 1"
2 3/4" (medium) circle - 3 oz per 1"
3 1/2" (large) circle - 5 oz per 1"
2" x 2 1/2" (medium) oval - 2 1/2 oz per 1"
2 1/2" x 3 1/2" (large) oval - 4 oz per 1"
1 1/2" (small) heart - 1 oz per 1"
3" (large) heart - 4 oz per 1"
1 1/2" (small) star - 1 oz per 1"
3" (large) star - 4 oz per 1"
1 1/2" (small) blossom - 1 oz per 1"
3" (large) star - 3 1/2 oz per 1"
2 1/2" butterfly - 3 1/2 oz per 1"
3" hexagon - 4 oz per 1"
3" x 4" (large) rectangle - 8 oz per 1"

Source: Designer Soapmaking by Marie Browning, Sterling Publishing, 2003. pg 23-24