Cost per Bomb
$0.50
Batch Weight
32.6 oz
Batch Cost
$2.98
You save $5.50–$9.50 per bomb vs retail prices
| Ingredient | oz | grams |
|---|---|---|
| Baking Soda | 2.45 | 69.4 |
| Citric Acid | 1.20 | 33.9 |
| Cornstarch | 0.71 | 20.0 |
| Epsom Salt | 0.44 | 12.3 |
| Carrier Oil | 0.44 | 12.3 |
| Fragrance Oil | 0.11 | 3.1 |
| Total | 5.44 | 154.2 |
Fragrance: ~64 drops per bomb
| Mold | Weight | DIY Cost | Retail |
|---|---|---|---|
| 1.75" sphere | ~1.9 oz | $0.15–$0.25 | $4–$6 |
| 2.5" sphere | ~5.4 oz | $0.45–$0.60 | $6–$8 |
| 3.15" sphere | ~10.9 oz | $0.85–$1.10 | $8–$12 |
Inputs
Result
Six standard bath bombs using the basic recipe need about 14.7 oz of baking soda and 7.2 oz of citric acid. At bulk ingredient prices, each bomb costs roughly $0.50 to make.
Inputs
Result
Twelve mini moisturizing bath bombs use about 9.0 oz of baking soda. At $0.19 each, a gift set of 12 costs just $2.22 in materials.
Inputs
Result
Four large extra-fizzy bath bombs require 21.8 oz of baking soda and 10.9 oz of citric acid. The extra citric acid makes these fizzier at $0.94 each.
The standard bath bomb ratio is 2:1 baking soda to citric acid by weight. A complete recipe breaks down to about 40–50% baking soda, 20–25% citric acid, 10–15% cornstarch, 5–10% Epsom salt, 5–10% carrier oil, and 1–3% fragrance oil. Adjusting the oil and cornstarch percentages changes how moisturizing or fizzy the bomb is.
| Ingredient | Basic % | Moisturizing % | Extra Fizzy % |
|---|---|---|---|
| Baking Soda | 45% | 40% | 50% |
| Citric Acid | 22% | 20% | 25% |
| Cornstarch | 13% | 12% | 10% |
| Epsom Salt | 8% | 8% | 8% |
| Carrier Oil | 8% | 15% | 3% |
| Fragrance Oil | 2% | 2% | 2% |
A single DIY bath bomb costs between $0.50 and $1.50 depending on size and ingredients. A standard 5.5 oz sphere (2.5" mold) costs roughly $0.70–$0.90 in materials. Retail bath bombs sell for $4–$12, so DIY saves 75–90% per bomb.
| Item | DIY Cost | Retail Price | Savings |
|---|---|---|---|
| Small (2 oz) | $0.30–$0.50 | $4–$6 | 85–92% |
| Standard (5.5 oz) | $0.70–$0.90 | $6–$8 | 85–90% |
| Large (9 oz) | $1.00–$1.50 | $8–$12 | 83–88% |
The most popular bath bomb mold is the 2.5-inch sphere, producing a 5.5–6.5 oz bomb that fits comfortably in a standard bathtub. Smaller 1.75-inch molds make 2 oz mini bombs ideal for gifts or kids. The 3.15-inch mold creates large 9 oz luxury bombs.
First calculate the total weight using sphere volume and density. Sphere volume is (4/3) × π × r³. Convert cubic inches to ounces using a density of about 1.15 g/cm³. Then multiply total weight by each ingredient percentage to get individual amounts.
Use 1–3% fragrance oil by total weight. For a standard 5.5 oz bath bomb, that is 0.06–0.17 oz (about 10–50 drops). Start at 2% and adjust based on scent strength. Skin-safe fragrance oils rated for bath products are essential — candle fragrances may irritate skin.
One pound (16 oz) of baking soda makes about 6–8 standard 5.5 oz bath bombs, since baking soda is roughly 45% of the recipe. For a batch of 12, you need about 2 lbs of baking soda, 1 lb of citric acid, and smaller amounts of fillers and oils.
Read our guide
Read our guide
Read our guide
Discover tools for candle making, soap crafting, resin art, fiber arts, and more.
Last Updated: Mar 9, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.