Article — Grams in mL Converter
Grams in mL: A Density-Based Conversion Guide
Grams measure mass; milliliters measure volume. Converting between them requires one piece of information: the density of the substance. For water, density is 1 g/mL, so 1 gram equals 1 milliliter exactly. For honey, density is about 1.42 g/mL, so 1 gram is only 0.70 mL. For olive oil at 0.91 g/mL, 1 gram is 1.10 mL. The formula is simple: mL = grams ÷ density.
About 14,500 monthly searches in English ask the grams-to-mL conversion. Most assume the 1-to-1 water relationship — and most pay for that assumption when they end up with too much oil, too little honey, or a flour measurement that is off by 40%. This guide walks through the density of every common kitchen and chemistry substance, with the math and the rules of thumb.
Grams to mL, the short version
The conversion is volume = mass ÷ density:
- Water (1.00 g/mL): grams = mL exactly. 100 g = 100 mL
- Milk (1.03 g/mL): 100 g = 97.1 mL. Within 3% of the water rule
- Olive oil (0.91 g/mL): 100 g = 109.9 mL. About 10% more volume per gram
- Honey (1.42 g/mL): 100 g = 70.4 mL. About 30% less volume per gram
- Ethanol (0.789 g/mL): 100 g = 126.7 mL. About 27% more volume per gram
- Flour (0.53 g/mL, loose): 100 g = 188.7 mL. Almost twice the volume of water
To go the other way (mL to grams), multiply: grams = mL × density. 250 mL of milk weighs 257.5 g. 250 mL of olive oil weighs 227.5 g. 250 mL of honey weighs 355 g.
The metric system was designed around water. In 1795, French scientists defined the kilogram as the mass of one litre of pure water at 4°C. That historical decision is why grams and milliliters are interchangeable for water — and only for water. Every other substance carries a density correction.
Why density is the entire story
Density is mass per unit volume — g/mL or g/cm³. Materials with tightly packed molecules (mercury at 13.6 g/mL, lead at 11.3 g/mL) have high densities. Materials with loosely packed molecules (ethanol at 0.789 g/mL, gasoline at 0.74 g/mL) have low densities. Water sits in the middle at 1.00 g/mL by definition.
That single number determines whether 1 gram is more or less than 1 milliliter. If density > 1, the substance is heavier than water for the same volume — so a gram takes up less than 1 mL. If density < 1, the substance is lighter than water for the same volume — so a gram takes up more than 1 mL. The sink/float behaviour you see in a glass of water is the same physics: density > 1 sinks, density < 1 floats.
Quick density check: drop the substance in water. Sinks = density > 1, fewer mL per gram than water. Floats = density < 1, more mL per gram than water. Olive oil floats. Honey sinks. Ethanol floats. Glycerin sinks.
Grams to mL for water
Water is the easy case. At 4°C, the density is exactly 1.00 g/mL by the 1795 metric definition. At 20°C (room temperature), it has dropped to 0.998 g/mL — a 0.2% error if you use the 1-to-1 rule. At 80°C (hot tap water), density drops to 0.972 g/mL — a 2.8% error. For everyday cooking, 1 g = 1 mL for water is exact enough.
The same near-1 rule works for most water-based liquids: milk (1.03 g/mL), juice (1.04), vinegar (1.01), beer (1.01), light cream (1.01). All of them are within 4% of water density, so for casual conversion the gram-equals-mL shortcut works fine.
Grams to mL for oil and honey
Oils and syrups are where the shortcut breaks. Olive oil is 0.91 g/mL — 9% less dense than water. A 100 g portion of olive oil takes up 110 mL of space, meaningfully more than 100 mL. For a recipe that calls for 250 g of oil, you would pour about 275 mL — a 25 mL gap that fills a small shot glass.
Honey runs the opposite direction. Pure honey is around 1.42 g/mL, 42% denser than water. A 500 g jar of honey occupies about 352 mL — about 150 mL less in volume than 500 g of water would be. The same applies to maple syrup (1.33 g/mL), corn syrup (1.38), and molasses (1.41). All three are dense sugar solutions: roughly 80% sugar by mass with the rest water.
If a recipe calls for 100 g of olive oil and you measure 100 mL, you have under-fat by 10%. If it calls for 100 g of honey and you measure 100 mL, you have over-honey by 42%. Both errors are large enough to change the outcome.
Grams to mL for flour and sugar
Dry kitchen ingredients add a second variable on top of density: how tightly the powder is packed. Loose-spooned all-purpose flour is about 0.53 g/mL. The same flour, scooped directly from a bag and tapped down, can hit 0.75 g/mL — a 40% range for the same nominal substance.
That is why professional bakers weigh flour rather than measuring it by volume. King Arthur Baking publishes 120 g per cup of flour as a target. Other cookbooks list 125 g. Packing methods can push the real weight to 175 g per cup. A bread recipe calling for 4 cups of flour might use 480 g or 700 g depending on technique — a 45% spread in the dough.
For granulated sugar (0.85 g/mL) the variability is smaller because sugar crystals do not compress easily. Salt at 1.22 g/mL is the densest common dry ingredient.
Temperature and the density curve
Density changes with temperature. Most substances expand when heated, so their density drops. The effect is small at kitchen room-temperature ranges (0–40°C) but big at cooking heat (180°C):
- Water 4°C: 1.000 g/mL (peak density)
- Water 20°C: 0.998 g/mL (room temperature)
- Water 100°C: 0.958 g/mL (boiling)
- Olive oil 20°C: 0.91 g/mL (room temperature)
- Olive oil 180°C: 0.81 g/mL (frying temperature)
- Honey 20°C: 1.42 g/mL (room temperature)
- Honey 40°C: 1.39 g/mL (warmed for pouring)
For most cooking, room-temperature density values are fine. For fryers, brewing, candy-making, or anything that runs at extreme heat, density tables for the working temperature give more accurate volume.
Common substance densities
Water 1.00 Milk 1.03Cream 1.01 Yogurt 1.02Olive oil 0.91 Veg oil 0.92Honey 1.42 Maple syrup 1.33Ethanol 0.789 Wine 0.99Flour 0.53 Sugar 0.85Kitchen rules of thumb
A few practical patterns that show up over and over:
- Water-like liquids (milk, juice, broth, vinegar): use g = mL within 4%
- Oils: divide grams by 0.92 (or multiply by 1.09) to get mL
- Honey and syrups: divide grams by 1.4 (or multiply by 0.71) to get mL
- Spirits and wines: divide grams by 0.95 (or multiply by 1.05) to get mL
- Flour: 1 cup ≈ 120–130 g loose, more if packed
- Sugar (granulated): 1 cup ≈ 200 g
- Butter: 1 stick = 113 g = 1/2 cup = 8 tbsp
The reason European recipes prefer grams while American recipes prefer cups is partly cultural and partly practical. Grams ignore density, packing, and humidity. Cups carry all three. Recipes written in grams are reproducible. Recipes written in cups depend on the cook's measuring technique.