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How to use Batch Math weight and percentage calculator

How to Use Batch Math

Weight, Percentage & Unit Converter for Makers

Batch Math is a simple calculator that helps you work with recipe numbers. Whether you need to figure out what percentage each ingredient is, convert a percentage-based recipe into actual weights, or switch between grams and ounces, Batch Math handles it all. It has three tabs, each designed for a different task.

The Three Tabs

1. Weight to %

Enter the weight of each ingredient and the calculator shows what percentage of the total batch each one makes up. Great for reverse-engineering a recipe or documenting a balm you created by feel.

2. % to Weight

Enter ingredient percentages and your desired batch weight, and the calculator tells you exactly how much of each ingredient to weigh out. Perfect for scaling recipes to any batch size.

3. Unit Convert

Convert an entire recipe from one unit to another (grams, ounces, pounds, or kilograms). Enter weights in the "from" unit and see them all converted to your "to" unit instantly.

How to Use: Weight to %

Use this when you have a recipe written in weights and want to know the percentages.

  1. Step 1: Choose your default unit (grams, ounces, pounds, or kilograms).
  2. Step 2: Type in each ingredient name and its weight.
  3. Step 3: If any ingredient uses a different unit, tap its unit dropdown to change it.
  4. Step 4: The percentage appears automatically next to each ingredient.
  5. Step 5: Use "+ Add Ingredient" to add more rows as needed.

Example: You have 300g olive oil, 150g coconut oil, and 50g castor oil. Enter each weight and the calculator shows 60%, 30%, and 10% respectively.

How to Use: % to Weight

Use this when you have a percentage-based recipe and need actual weights for a specific batch size.

  1. Step 1: Enter your desired total batch weight (e.g., 500) and choose the unit.
  2. Step 2: Type each ingredient name and its percentage.
  3. Step 3: The weight for each ingredient appears automatically.
  4. Step 4: Check the total percentage — it should equal 100% for a complete formula.

Example: A lotion formula calls for 70% water, 15% oil, 10% emulsifier, and 5% actives. Set batch weight to 200g and the calculator shows 140g, 30g, 20g, and 10g.

How to Use: Unit Convert

Use this when you need to convert a recipe from one measurement system to another.

  1. Step 1: Choose your "From" unit (the unit your recipe is currently in).
  2. Step 2: Choose your "To" unit (what you want to convert to).
  3. Step 3: Enter each ingredient name and weight in the "from" unit.
  4. Step 4: The converted weight appears next to each ingredient.
Tip: Use the swap button to quickly reverse the conversion direction.

Common Use Cases

Scaling up for production: You perfected a 100g test batch of lotion. Use % to Weight with a larger batch size (e.g., 1000g) to scale up.
Documenting a recipe: You created a soap recipe by feel. Weigh what's left, enter the amounts in Weight to %, and save the percentages for next time.
Following a foreign recipe: You found a recipe in grams but your scale reads ounces. Use Unit Convert to switch units for every ingredient at once.
Sharing formulas: Percentages are universal. Convert your weight-based recipe to percentages so others can make any batch size they want.

Tips for Accurate Batching

  • Always use a digital scale for weighing — measuring cups are not accurate enough for formulation.
  • Account for loss: make your batch slightly larger (2-5% extra) to compensate for what sticks to containers and utensils.
  • Round to your scale's precision. If your scale reads to 0.1g, round the calculated weights to one decimal place.
  • Keep a notebook: record the batch weight and date each time you make a recipe so you can track improvements.

Frequently Asked Questions

Related Resources

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