The Candle Wax & Fragrance Oil Formula, Explained
Candle making math involves two linked calculations: how much wax fills your container by weight, and how much fragrance oil to add relative to that wax weight.
| Step | Formula |
|---|---|
| Container Volume (cylinder) | V = π × r² × Fill Height |
| Container Volume (rectangle) | V = Length × Width × Fill Height |
| Wax Weight | Weight = V (mL) × Wax Density (g/mL) |
| Fragrance Oil Weight | FO Weight = Wax Weight × Fragrance Load % |
Note that "fill height" should reflect how far up the container you actually intend to pour wax, not the container's full physical height — most candle makers leave roughly 1/4 to 1/2 inch of headspace below the rim.
Step-by-Step Calculation Example
Let's manually calculate a batch of 6 soy wax candles poured into cylindrical jars that are 3 inches in diameter, filled to a height of 3.5 inches, using an 8% fragrance load.
- Find the radius: 3 ÷ 2 = 1.5 inches.
- Calculate per-jar volume: π × 1.5² × 3.5 = 24.74 cubic inches.
- Convert to milliliters: 24.74 × 16.387 = 405.5 mL per jar.
- Multiply by jar count: 405.5 × 6 = 2,433 mL total volume.
- Calculate total wax weight (soy, 0.90 g/mL): 2,433 × 0.90 = 2,189.7 g.
- Calculate fragrance oil weight (8% load): 2,189.7 × 0.08 = 175.2 g.
That's roughly 2,190 grams (about 77 oz) of soy wax and 175 grams (about 6.2 oz) of fragrance oil for the full batch of 6 jars — try entering these same values into the calculator above to confirm.
Conversion & Reference Tables
Wax Density by Type
| Wax Type | Density (g/mL) | Typical Fragrance Load |
|---|---|---|
| Soy Wax | 0.90 | 6 – 10% |
| Paraffin Wax | 0.90 | 6 – 12% |
| Beeswax | 0.96 | 3 – 5% |
| Coconut Wax | 0.92 | 6 – 10% |
Common Container Sizes
| Container | Approx. Fill Volume |
|---|---|
| 4 oz tin | ~110 mL |
| 8 oz jar (standard) | ~225 mL |
| 9 oz tumbler jar | ~255 mL |
| 16 oz jar (large) | ~450 mL |
Troubleshooting & Practical Usage Tips
Measuring by Volume vs. Weight
Candle recipes should always be measured by weight (grams or ounces on a scale), not by volume (measuring cups). Wax density varies enough between types — and even between batches — that volume measurements introduce meaningful error, especially at scale across many containers.
Thermal Shrinkage & Frosting
Soy and coconut waxes are prone to visible shrinkage as they cool and to a natural crystalline "frosting" effect on the surface. Pouring at your wax's recommended temperature and cooling candles slowly at consistent room temperature (avoiding cold drafts or refrigeration) reduces both effects.
Room Temperature Factors
Fragrance oil binds best to wax within a specific temperature window (commonly 175–185°F for soy wax) — adding it too hot can cause the scent to evaporate off before the candle sets, while adding it too cool can cause poor binding and scent throw. Always check your specific wax manufacturer's recommended fragrance-addition temperature.
Common Mistakes to Avoid
- Exceeding your wax's maximum fragrance load, which can cause the oil to "sweat" out of the finished candle.
- Forgetting to account for wick and label placement time, causing wax to set before pouring is finished.
- Not accounting for wax that clings to your melting pot and stir utensils when calculating batch totals — budget 5–10% extra wax for larger batches.
- Using a fill height equal to the container's full height instead of leaving headspace below the rim.