Grams to Fluid Ounces Formula
The complete mathematical guide to converting between grams (mass) and fluid ounces (volume), with step-by-step examples for every common ingredient.
The Core Formula
Converting grams to fluid ounces requires dividing by the substance's density and the milliliters-per-fluid-ounce constant:
fl oz = grams ÷ (density × 29.5735) Where:
- grams = the mass you want to convert
- density = substance density in g/mL (see table below)
- 29.5735 = milliliters per 1 US fluid ounce (NIST standard)
Simplified Formula for Water
Since water has a density of exactly 1.0 g/mL at standard conditions, the formula simplifies to:
fl oz = grams ÷ 29.5735 This means 1 gram of water = 0.033814 US fluid ounces.
Step-by-Step Examples
Example 1: 250g of Water
- Density: Water = 1.0 g/mL
- Apply formula: 250 ÷ (1.0 × 29.5735)
- Calculate: 250 ÷ 29.5735 = 8.4535 US fl oz
Example 2: 200g of Flour
- Density: All-purpose flour = 0.529 g/mL
- Apply formula: 200 ÷ (0.529 × 29.5735)
- Calculate: 200 ÷ 15.645 = 12.78 US fl oz
Example 3: 100g of Honey
- Density: Honey = 1.42 g/mL
- Apply formula: 100 ÷ (1.42 × 29.5735)
- Calculate: 100 ÷ 41.994 = 2.38 US fl oz
The Reverse Formula: Fluid Ounces to Grams
To convert in the other direction:
grams = fl oz × density × 29.5735 For water: grams = fl oz × 29.5735. So 8 fl oz of water = 8 × 29.5735 = 236.59 grams.
Ingredient Density Reference
Use these density values in the formula for accurate conversions:
| Ingredient | Density (g/mL) | 100g → US Fl Oz | 1 Fl Oz → Grams |
|---|---|---|---|
| 💧 Water | 1 | 3.38 fl oz | 29.57g |
| 🥛 Whole Milk | 1.03 | 3.28 fl oz | 30.46g |
| 🫒 Cooking Oil | 0.92 | 3.68 fl oz | 27.21g |
| 🌾 All-Purpose Flour | 0.529 | 6.39 fl oz | 15.64g |
| 🍚 Granulated Sugar | 0.845 | 4.00 fl oz | 24.99g |
| 🧈 Melted Butter | 0.959 | 3.53 fl oz | 28.36g |
| 🍯 Honey | 1.42 | 2.38 fl oz | 41.99g |
| 🍷 Alcohol (Ethanol) | 0.789 | 4.29 fl oz | 23.33g |
US vs Imperial Fluid Ounces
For UK Imperial fluid ounces, use 28.4131 instead of 29.5735:
Imperial fl oz = grams ÷ (density × 28.4131) The Imperial fluid ounce is about 4.1% smaller than the US fluid ounce, so the same mass converts to slightly more Imperial fl oz.
Why Density Matters
Grams measure mass (how much matter), while fluid ounces measure volume (how much space). Converting between them is like asking "how many boxes does this weight fill?" — it depends on how heavy the stuff is per box.
Example: 100g of flour takes up 6.39 fl oz of space, while 100g of honey only fills 2.38 fl oz. Same weight, vastly different volumes — because honey is 2.7× denser than flour.