Soap Mold Volume Calculator
Volume of a rectangular, cylindrical or loaf soap mould in cubic inches and millilitres, and the batter weight it holds at 0.4 ounces per cubic inch.
At a glance
- What you enter
- Mould shape, Inside length, Inside width, Inside diameter, Depth you fill to, Weight of one bar, Batter lost to trimmings, Water as a percentage of oils, Fragrance or essential oil load, Lye solution, as a percentage of the oil weight
- What you get
- Mould volume, Mould volume, Batter the mould holds, Batter the mould holds, Batter that becomes bars, Whole bars the mould makes
- Formula shown
- Yes, every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
Results are estimates for general information only, always verify with a professional or official source before acting on them.
How to use the Soap Mold Volume Calculator
- 1 Enter Mould shape
- 2 Enter Inside length (in), Rectangular and loaf moulds.
- 3 Enter Inside width (in), Rectangular and loaf moulds.
- 4 Enter Inside diameter (in), Cylindrical moulds, measured across the inside.
- 5 Enter Depth you fill to (in), The height you actually fill to, not necessarily the full height of the mould.
- 6 Enter Weight of one bar (oz), Used to turn the volume into a bar count.
- 7 Enter Batter lost to trimmings (%), The ends, the top and the bit that stays in the pot.
- 8 Enter Water as a percentage of oils (%), Only used for the rough oil estimate. Cold process recipes usually sit between 33 and 38 percent.
- 9 Enter Fragrance or essential oil load (%), Only used for the rough oil estimate, as a percentage of the oil weight.
- 10 Enter Lye solution, as a percentage of the oil weight (% of oil weight), Used only for the rough oil estimate. The real alkali figure comes from a lye calculator.
- 11 Press Calculate. You get Mould volume, Mould volume, Batter the mould holds, Batter the mould holds, Batter that becomes bars, Whole bars the mould makes, and every intermediate step stays visible under "How is this calculated?"
- 12 Change one number at a time to see what moves the result, that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
Standard ten inch loaf mould
A 10 by 3.5 by 2.5 inch loaf, filled to the top, cut into 4.4 ounce bars.
You enter
- Mould shape
- 1
- Inside length
- 10 in
- Inside width
- 3.50 in
- Inside diameter
- 3 in
- Depth you fill to
- 2.50 in
- Weight of one bar
- 4.40 oz
- Batter lost to trimmings
- 8%
- Water as a percentage of oils
- 35%
- Fragrance or essential oil load
- 6%
- Lye solution, as a percentage of the oil weight
- 38%
You get
- Mould volume
- 87.50 cu in
- Mould volume
- 1,433.87 mL
- Batter the mould holds
- 35.00 oz
- Batter the mould holds
- 992.23 g
- Batter that becomes bars
- 32.20 oz
- Whole bars the mould makes
- 7
Eighty seven and a half cubic inches, about 1,434 millilitres and 35 ounces of batter, which is seven full bars once the ends are trimmed.
Three inch PVC pipe mould
A 3 inch inside diameter pipe filled to 12 inches, cut into 4 ounce rounds.
You enter
- Mould shape
- 2
- Inside length
- 10 in
- Inside width
- 3.50 in
- Inside diameter
- 3 in
- Depth you fill to
- 12 in
- Weight of one bar
- 4 oz
- Batter lost to trimmings
- 5%
- Water as a percentage of oils
- 35%
- Fragrance or essential oil load
- 6%
- Lye solution, as a percentage of the oil weight
- 38%
You get
- Mould volume
- 84.82 cu in
- Mould volume
- 1,390.00 mL
- Batter the mould holds
- 33.93 oz
- Batter the mould holds
- 961.88 g
- Batter that becomes bars
- 32.23 oz
- Whole bars the mould makes
- 8
About 84.8 cubic inches, so 33.9 ounces of batter and eight rounds of about 4 ounces.
Small one pound test mould
A 6 by 2.5 by 2 inch mould for a test batch.
You enter
- Mould shape
- 1
- Inside length
- 6 in
- Inside width
- 2.50 in
- Inside diameter
- 3 in
- Depth you fill to
- 2 in
- Weight of one bar
- 4 oz
- Batter lost to trimmings
- 10%
- Water as a percentage of oils
- 35%
- Fragrance or essential oil load
- 6%
- Lye solution, as a percentage of the oil weight
- 38%
You get
- Mould volume
- 30.00 cu in
- Mould volume
- 491.61 mL
- Batter the mould holds
- 12.00 oz
- Batter the mould holds
- 340.19 g
- Batter that becomes bars
- 10.80 oz
- Whole bars the mould makes
- 2
Thirty cubic inches, so 12 ounces of batter, which is two or three bars. A good size for testing a new fragrance.
Guides that go with it
How to Avoid Wasting Materials When Making Crafts
Most craft waste is not caused by clumsy hands. It is caused by decisions made before you pick up a tool: buying too much, cutting before measuring, or starting a project with no plan for the offcuts....
Simple Tricks for Making Handmade Items More Durable
A handmade piece that falls apart in six months is a disappointment, not an heirloom. By the end of this guide you will know how to build durability into a project from the first cut to the final coat...
How to Choose the Right Materials for Your Handcraft Project
Picking materials is where most beginner projects are won or lost. Choose well and the making feels easy; choose badly and you fight the supplies the whole way. By the end of this guide you will know...
Frequently asked questions
How much soap batter does my mould hold?
Where does the 0.4 ounces per cubic inch rule come from?
How many bars will a loaf mould make?
Should I measure the mould to the rim or to the fill line?
Can I work out the oil weight from the mould volume?
Terms used here
Short, plain-language definitions of the words this calculator uses.