Melt and Pour Calculator
Estimate how much melt-and-pour soap base your mould needs from cavity volume, count, fill level and base density, plus the fragrance to add. Calculates in your browser.
Total base needed
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Show the math
Each cavity holds a volume of base; weight is that volume times the base's density, allowing for a fill short of the brim:
base / cavity = volume × (fill ÷ 100) × density
total base = base / cavity × cavities · fragrance = total × load ÷ 100
Melt-and-pour base is pre-saponified, so there's no lye to handle, but it can scorch. Melt gently in short bursts, keep fragrance within your base's recommended limit so it doesn't sweat or seize, and pour at the temperature your base specifies.
What this does
A melt and pour calculator estimates how much soap base your mould needs from cavity volume, count, fill level, and base density, plus the fragrance to add.
How to use it
- Enter the cavity volume and count.
- Set the fill level.
- Enter the base density.
- Read the base weight and fragrance.
How it works
Melt-and-pour base is around 0.95 g/mL. It is already saponified, so there is no lye — just keep fragrance within the base’s recommended limit.
base = volume × fill ÷ 100 × density × cavities
Understanding your result
Melt-and-pour base is already saponified, so there is no lye and no cure to worry about, but it still has a recommended fragrance limit, so keep additions within it or the bars sweat and lose firmness. The base figure assumes your fill level, so leave a little headroom in each cavity, and overestimate slightly since some base always coats the pouring jug.
Example
Six 80 mL cavities filled to 95% need about 433 g of base.
Sources & methodology
Last updated .
Frequently asked questions
How much base will I need?
Base per cavity = volume × fill ÷ 100 × density, multiplied by the number of cavities. Melt-and-pour base is around 0.95 g/mL by default.
How do I find my cavity volume?
If you don’t know it, fill one cavity with water and weigh it — grams of water roughly equals millilitres of volume.
Do I handle lye with melt and pour?
No — the base is already saponified, so there’s no lye. Just melt gently and keep fragrance within the base’s recommended limit.
Is my data saved?
No — every calculation happens locally in your browser.
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