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Soap Batch Scaling Calculator

Scale a soap recipe up or down by a factor or to a target number of bars, keeping every percentage in step.

Soap Making
A recipe that makes eight bars and an order for thirty is a scaling job, and scaling soap is not just multiplying the oil weight. Water, fragrance and lye all follow the oils as percentages, and a bigger batch needs a little spare. This calculator scales every line by the same factor, shows the factor it used, and gives the batch its new total weight so the pot and the moulds can be checked before anything is measured out.

At a glance

What you enter
Scale by, Bars the recipe makes, Bars you want, Batter the recipe makes, Batter you want, Oils in the original recipe, Water as a percentage of oils, Fragrance or essential oil load, Lye solution planning figure, Extra batter to prepare
What you get
Oils for the scaled batch, Oils for the scaled batch, Water for the scaled batch, Fragrance or essential oil, Batter the scaled recipe makes, Batter to prepare, Batter to prepare in grams
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 ↓

Scale by

Choose whether the original recipe is described by the bars it makes or by the weight of batter it produces.

Used when scaling by bar count.

Used when scaling by bar count.

Used when scaling by batch weight.

Used when scaling by batch weight.

Weight, from your recipe or from the batch size calculator.

The figure the original recipe uses, so it carries across to the scaled batch.

A percentage of the oil weight. Your supplier's usage rate for that oil governs.

Used only to put a planning weight on the lye line. The real lye figure comes from a lye calculator.

Covers what stays in the pot and what is lost at the pour.

Reset

Results are estimates for general information only, always verify with a professional or official source before acting on them.

How to use the Soap Batch Scaling Calculator

  1. 1 Enter Scale by, Choose whether the original recipe is described by the bars it makes or by the weight of batter it produces.
  2. 2 Enter Bars the recipe makes (bars), Used when scaling by bar count.
  3. 3 Enter Bars you want (bars), Used when scaling by bar count.
  4. 4 Enter Batter the recipe makes (oz), Used when scaling by batch weight.
  5. 5 Enter Batter you want (oz), Used when scaling by batch weight.
  6. 6 Enter Oils in the original recipe (oz), Weight, from your recipe or from the batch size calculator.
  7. 7 Enter Water as a percentage of oils (%), The figure the original recipe uses, so it carries across to the scaled batch.
  8. 8 Enter Fragrance or essential oil load (%), A percentage of the oil weight. Your supplier's usage rate for that oil governs.
  9. 9 Enter Lye solution planning figure (%), Used only to put a planning weight on the lye line. The real lye figure comes from a lye calculator.
  10. 10 Enter Extra batter to prepare (%), Covers what stays in the pot and what is lost at the pour.
  11. 11 Press Calculate. You get Oils for the scaled batch, Oils for the scaled batch, Water for the scaled batch, Fragrance or essential oil, Batter the scaled recipe makes, Batter to prepare, Batter to prepare in grams, and every intermediate step stays visible under "How is this calculated?"
  12. 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.

Eight bars scaled to thirty

A usual eight bar recipe scaled up to a thirty bar market batch.

You enter

Scale by
1
Bars the recipe makes
8
Bars you want
30
Batter the recipe makes
35 oz
Batter you want
120 oz
Oils in the original recipe
25 oz
Water as a percentage of oils
35%
Fragrance or essential oil load
6%
Lye solution planning figure
38%
Extra batter to prepare
5%

You get

Oils for the scaled batch
93.75 oz
Oils for the scaled batch
5.86 lb
Water for the scaled batch
32.81 oz
Fragrance or essential oil
5.63 oz
Batter the scaled recipe makes
167.81 oz
Batter to prepare
176.20 oz
Batter to prepare in grams
4,995.27 g

A factor of 3.75, so about 93.75 ounces of oils and 137 ounces of batter to prepare. Check the pot before you commit.

Open this example in the calculator →

A recipe halved

A loaf recipe scaled down to a single test mould.

You enter

Scale by
1
Bars the recipe makes
8
Bars you want
4
Batter the recipe makes
35 oz
Batter you want
120 oz
Oils in the original recipe
25 oz
Water as a percentage of oils
35%
Fragrance or essential oil load
6%
Lye solution planning figure
38%
Extra batter to prepare
5%

You get

Oils for the scaled batch
12.50 oz
Oils for the scaled batch
0.78 lb
Water for the scaled batch
4.38 oz
Fragrance or essential oil
0.75 oz
Batter the scaled recipe makes
22.38 oz
Batter to prepare
23.49 oz
Batter to prepare in grams
666.04 g

A factor of 0.5, so about 12.5 ounces of oils. Small batches trace quickly, so have the mould ready.

Open this example in the calculator →

Scaling by batch weight

A recipe that produces a 35 ounce loaf, scaled to a 70 ounce slab mould.

You enter

Scale by
2
Bars the recipe makes
8
Bars you want
30
Batter the recipe makes
35 oz
Batter you want
70 oz
Oils in the original recipe
25 oz
Water as a percentage of oils
35%
Fragrance or essential oil load
6%
Lye solution planning figure
38%
Extra batter to prepare
5%

You get

Oils for the scaled batch
50.00 oz
Oils for the scaled batch
3.13 lb
Water for the scaled batch
17.50 oz
Fragrance or essential oil
3.00 oz
Batter the scaled recipe makes
89.50 oz
Batter to prepare
93.98 oz
Batter to prepare in grams
2,664.15 g

A factor of 2, so 50 ounces of oils and 74.5 ounces of batter to prepare for a 70 ounce mould.

Open this example in the calculator →

Guides that go with it

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Frequently asked questions

How do I scale a soap recipe up or down?
Divide the target by the original to get a factor, then multiply every material by it. Eight bars scaled to thirty is 3.75, so 25 ounces of oils becomes 93.75 ounces. Then recalculate water, fragrance and lye as the same percentages of the new oil weight, rather than multiplying their original weights, so the recipe stays in proportion. Add a little spare for the pot, and check the pot and the moulds can take the bigger batch before you start.
Can I just double a soap recipe?
The proportions are safe to double, and the arithmetic is the same factor of two, but the batch behaves differently. A double batch heats up faster and gels differently, takes longer to trace, and needs moulds and a pot that can hold it. For a batch much bigger than your usual one, work in two batches rather than one giant one, and check the new formulation in a lye calculator rather than scaling the lye weight by hand.
Why does water scale with the oils rather than as its own weight?
Because a soap recipe states water as a percentage of the oil weight, so water is part of the ratio rather than a fixed amount. If the oils scale by 3.75, the water scales by 3.75 as well because it is 35 percent of a number that is 3.75 times bigger. This tool calculates the scaled water from the scaled oil weight, which is the same thing and leaves less room for a slip.
How much extra batter should I prepare for a bigger batch?
Five percent is enough for a batch you make often, and 10 percent is sensible when you are scaling up to a size you have not poured before. At 120 ounces of batter, five percent is six ounces, which is more than one bar of spare. Scaling up usually means a bigger pot, more pouring and a longer time before the batter reaches the mould, so the losses are larger than they are on your usual batch.
Is the lye figure on this page something I can use?
No. It is a planning weight so that a scaled batch has a number against the lye line for costing and pot sizing. A real lye weight depends on the saponification values of the specific oils in the specific proportions, and on the superfat, and it must come from a reliable lye calculator. Run the scaled recipe through one before you measure anything, and follow the alkali supplier's safety data sheet.

More money questions answered →

Terms used here

Short, plain-language definitions of the words this calculator uses.

Water discount Using less water in a soap recipe than the standard amount, expressed as a percentage of the oil weight rather than as a proportion of the alkali.

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