Soap Recipe Resize Calculator
Everything in a soap recipe moves together: 1.5× the oil is 1.5× the lye and 1.5× the water. Mould volume is the easy way to pick the factor — a 1,200 mL mould going to 1,800 mL is 1.5×. A recipe of 500 g oil, 65 g lye and 130 g water scaled by 1.5 becomes 750 g, 97.5 g and 195 g.
Your numbers
Oil weight
750g
Lye needed
97.5g
Water
195g
Batter total
1,043g
Formula
Oil weight = Oil weight × Recipe scale
Do not recalculate the lye from scratch, just scale it — the SAP has not changed while the oils are the same. Do expect the behaviour to change: a bigger batch holds its heat longer and thickens faster, and strong colours or fragrances speed that up further. Swap an oil and it is the SAP, not the scale, that has to be redone.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Oil weight (g)Total oils in the recipe, excluding water and lye. | 500 | 1 and up |
| Lye needed (g)Lye needed; too little leaves it soft, too much leaves it caustic. | 65 | 0 and up |
| Water (g)Water to dissolve in; lye goes into water, never the reverse. | 130 | 0 and up |
| Recipe scale (×)How many times the recipe you are making. | 1.5 | 0.1 ~ 20 |
Step by step
Quick reference table
Results when only Oil weight (g) changes and everything else stays put.
| Oil weight (g) | Oil weight (g) | Lye needed (g) | Water (g) |
|---|---|---|---|
| 250 | 375 | 97.5 | 195 |
| 375 | 562.5 | 97.5 | 195 |
| 500 | 750 | 97.5 | 195 |
| 750 | 1,125 | 97.5 | 195 |
| 1,000 | 1,500 | 97.5 | 195 |
What each result means
| Result | At default values |
|---|---|
| Oil weight (g)Total oils in the recipe, excluding water and lye. | 750 |
| Lye needed (g)Lye needed; too little leaves it soft, too much leaves it caustic. | 97.5 |
| Water (g)Water to dissolve in; lye goes into water, never the reverse. | 195 |
| Batter total (g)Oils, water and lye together. | 1,043 |
Common mistakes
Do not recalculate the lye from scratch, just scale it — the SAP has not changed while the oils are the same. Do expect the behaviour to change: a bigger batch holds its heat longer and thickens faster, and strong colours or fragrances speed that up further. Swap an oil and it is the SAP, not the scale, that has to be redone.
Glossary
- Oil weight
- Total oils in the recipe, excluding water and lye.
- Lye needed
- Lye needed; too little leaves it soft, too much leaves it caustic.
- Water
- Water to dissolve in; lye goes into water, never the reverse.
- Recipe scale
- How many times the recipe you are making.
- Batter total
- Oils, water and lye together.
Frequently asked questions
Q. How is Soap Recipe Resize Calculator calculated?
Oil weight = Oil weight × Recipe scale — Everything in a soap recipe moves together: 1.5× the oil is 1.5× the lye and 1.5× the water. Mould volume is the easy way to pick the factor — a 1,200 mL mould going to 1,800 mL is 1.5×. A recipe of 500 g oil, 65 g lye and 130 g water scaled by 1.5 becomes 750 g, 97.5 g and 195 g.
Q. Can you walk through an example?
With Oil weight 500g, Lye needed 65g, Water 130g, Recipe scale 1.5×, the answer is Oil weight 750g.
Q. What do I need to enter?
Enter Oil weight, Lye needed, Water, Recipe scale. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Oil weight (g) moves the answer to Oil weight (g) 250 → Oil weight (g) 375 and Oil weight (g) 1,000 → Oil weight (g) 1,500. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Do not recalculate the lye from scratch, just scale it — the SAP has not changed while the oils are the same. Do expect the behaviour to change: a bigger batch holds its heat longer and thickens faster, and strong colours or fragrances speed that up further. Swap an oil and it is the SAP, not the scale, that has to be redone.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.