Article — Grams to mL Converter
Grams to mL: Why the Conversion Depends on the Substance
To convert grams to millilitres, divide the mass in grams by the density of the substance in grams per millilitre. For water, density is 1.00 g/mL and the numbers are equal. For other substances, the result is different: 100 g of honey (1.42 g/mL) is 70 mL, 100 g of flour (0.53 g/mL) is 189 mL, 100 g of olive oil (0.91 g/mL) is 110 mL.
The conversion question is common because grams and millilitres are the two metric units that show up most often in recipes, on food labels, and in lab protocols — and they measure different things. Grams measure mass, what a scale reads. Millilitres measure volume, what a measuring cup reads. Treating them as interchangeable is the single most common kitchen-conversion mistake.
Why grams to mL is not 1:1
Mass and volume are different physical quantities. Mass is the amount of matter in an object; volume is the space it occupies. The two are related through density, which is mass per unit volume. The same volume of two different substances holds different masses. A litre of water weighs 1 kg, but a litre of mercury weighs 13.5 kg.
The 1:1 rule for grams and mL only holds for water, and only at the temperature where water is densest (4°C). At that single condition, the metric system was originally defined so that one cubic centimetre of water has a mass of one gram. Everything else inherits its own conversion factor through its own density.
The Académie des Sciences fixed the kilogram in 1795 as the mass of one cubic decimetre (one litre) of water at the temperature where water is densest. The choice tied the entire metric mass system to a substance every laboratory had on tap. The kilogram was redefined in 2019 in terms of the Planck constant, but for any cooking or kitchen-scale work, the water-gram-millilitre relationship is unchanged.
Density: the bridge from grams to mL
Every gram-to-mL conversion uses one number, the density of the substance. Density is published for every common substance in reference databases: USDA FoodData Central for foods, NIST for laboratory chemicals, FAO/INFOODS for international nutrition work. The dropdown in this converter is loaded from those sources.
The math is one division. To go from grams to mL, divide grams by density. To go from mL to grams, multiply mL by density. The calculator does this in both directions and updates the field you are not typing in.
- Water 1.00 g/mL (definition at 4°C)
- Whole milk 1.03 g/mL (proteins and lactose add weight)
- Olive oil 0.91 g/mL (lighter than water, like all oils)
- Honey 1.42 g/mL (densest common kitchen liquid)
- Maple syrup 1.33 g/mL (close to honey)
- All-purpose flour 0.53 g/mL (loose, with air gaps)
- Granulated sugar 0.85 g/mL (uniform crystals pack well)
- Brown sugar (packed) 0.92 g/mL (moisture binds crystals)
- Cocoa powder 0.40 g/mL (very fine, lots of air)
- Ethanol 0.79 g/mL (the lightest common liquid)
Water and the 1:1 special case
Water is the reference. 1 g of water at 4°C occupies exactly 1 mL by the original definition of the kilogram, and to within 0.4% at any temperature between 0°C and 100°C. For everyday cooking, treating water as a 1:1 grams-to-mL conversion is correct to the precision a kitchen scale can read.
The kitchen-water 1:1 rule extends approximately to dilute aqueous solutions. Tea, coffee, broth, and stock are all 98–99% water by mass and have densities within 1% of pure water. For practical recipe work they can all be converted at 1 g = 1 mL. Sugar syrups break the rule: a heavy simple syrup at 60% sugar has density 1.29 g/mL, closer to honey than to water.
Cooking and baking ingredients
Recipes that travel between countries usually need a grams-to-mL conversion somewhere along the way. European recipes give ingredient weights in grams; American recipes give volumes in cups, tablespoons, and teaspoons. Switching the same recipe between the two systems means converting each ingredient through its own density.
The most-converted ingredients are flour, sugar, butter, oil, milk, and honey. Each has a published density and the math is straightforward. The complication is that recipe accuracy varies with ingredient: liquid measurements are reproducible to within 2–3%, dry-ingredient measurements vary by 20% or more depending on how the cup was filled.
When converting an American recipe to grams, weigh the ingredient the first time you make the dish at home. Note the actual gram weight on the recipe card. The next time you make it, weight gives a more reproducible result than re-measuring by volume. Professional bakeries operate entirely on weighed ingredients, and the standardisation is the main reason their products are consistent.
Laboratory and pharmaceutical use
Chemistry and pharmacy use grams-to-mL conversions when a solid reagent needs to be dissolved into a known volume of solvent. The mass goes on the balance in grams, the solvent goes in the flask in millilitres, and the resulting solution concentration is reported in grams per litre (or molarity, after converting through molar mass). The bridge between mass and volume is the density of the final solution, not the density of the dry reagent.
Pharmaceutical formulations also use density for liquid medications. A cough syrup at density 1.20 g/mL means 10 mL of syrup weighs 12 g. Density appears on the data sheet for every liquid drug because the manufacturing process measures by mass on a precision balance but the patient receives a measured volume.
The flour density problem
Flour is the ingredient where grams-to-mL conversion goes wrong most often. The published density of 0.53 g/mL assumes flour was spooned gently into the measure and the top struck off level. If the cook scoops the measuring cup directly into the flour bag, the packing rises and density climbs to about 0.65 g/mL. Sifted flour falls to 0.45 g/mL.
That is a 44% spread for the same flour. The same gram weight translates to a different volume depending on how the flour was handled. The standard density values used here are FAO/INFOODS averages for spooned flour; if a recipe specifies scooped or sifted, the volume changes accordingly.
The grams-to-mL conversion for flour is only as good as the density assumption. A 200 g recipe converts to 377 mL of spooned flour, 308 mL of scooped flour, or 444 mL of sifted flour. If the recipe does not say, default to spooned. The volume difference is bigger than the per-cup tolerance of most US measuring cups.
Temperature corrections
Liquid densities change with temperature, and grams-to-mL conversions inherit the change. Water density drops from 1.000 g/mL at 4°C to 0.958 g/mL at 100°C — a 4% reduction. Cooking oils expand faster, about 0.07% per °C. Hot frying oil at 180°C is roughly 11% less dense than at room temperature.
For kitchen work the temperature correction is negligible. For lab work and food science, density tables are quoted at 20°C as the standard reference temperature. The calculator uses 20°C values throughout.