Is Cornflour the Same as Cornstarch? UK Guide and Keto Thickeners
Yes. UK cornflour is the same as US cornstarch: a fine, bright white starch extracted from maize. You can swap them spoon for spoon. What Americans call corn flour is different: whole maize ground into a yellow flour, closer to UK maize flour or fine cornmeal. Cornflour is almost pure starch, with 92.0g carbs per 100g.
At a glance
- 1:1use UK cornflour wherever a US recipe says cornstarch
- 92.0gcarbs per 100g of cornflour (CoFID)
- ~6.4gcarbs in a level tablespoon of cornflour
- A pinchof xanthan gum thickens a sauce instead
On this page
American recipes ask for cornstarch, British ones ask for cornflour, and then there's "corn flour", cornmeal, polenta and maize flour on top. It's one of the most confusing bits of UK and US kitchen vocabulary, and picking the wrong bag can turn a smooth gravy into a gritty one.
This guide clears up which is which, shows how many carbs cornflour adds, and explains the low-carb ways to thicken sauces, gravies and custards if you're cooking keto.
Is cornflour the same as cornstarch?
Yes. Cornflour is the British name and cornstarch (or corn starch) is the American name for the same ingredient. It's the starch extracted from the endosperm, the white, starchy centre of the maize kernel, then dried and milled into a very fine, squeaky white powder.
Because it's almost pure starch, it has no real flavour and no colour. That makes it a useful thickener: when you heat it in a liquid, the starch granules swell and the liquid turns thick and glossy. UK cooks use it for gravy, white sauces, stir-fry sauces, fruit fillings and custard, and in small amounts in shortbread and sponges to soften the crumb.
So if a US recipe calls for 2 tablespoons of cornstarch, use 2 tablespoons of UK cornflour. No conversion is needed. You may also see it on ingredients lists as maize starch or modified maize starch, which is cornflour that has been treated so it copes better with heating, freezing or acid.
UK custard powder is mostly cornflour with colouring and flavouring. The UK's food composition data (CoFID) uses the same carb figures for custard powder as for cornflour.
Cornflour, corn flour, cornmeal and polenta
The real trap is the American corn flour, written as two words. In the US, that means whole dried maize kernels ground into a fine, yellow flour. It contains the whole grain, so it has a mild corn flavour and doesn't thicken a sauce the way pure starch does. Here's how the names line up:
| UK name | US name | What it is | Used for |
|---|---|---|---|
| Cornflour | Cornstarch | Pure white maize starch | Thickening sauces, gravy, custard |
| Maize flour | Corn flour | Whole maize, finely ground | Cornbread, batters, flatbreads |
| Cornmeal | Cornmeal | Whole maize, more coarsely ground | Cornbread, coatings, muffins |
| Polenta | Polenta, grits | Coarse maize meal, or the cooked dish | Soft or set polenta |
| Masa harina | Masa harina | Maize treated with lime, then ground | Tortillas, tamales |
Names vary between brands and shops, so check the ingredients and the colour. Cornflour is bright white and squeaky; the others are yellow or cream and feel more like flour or fine sand.
If a US recipe says "corn flour" in a cornbread or batter, look for maize flour or fine cornmeal in the world food aisle, not the white cornflour in the baking aisle. If it says "cornstarch", it means UK cornflour.
Cornflour is made from maize, not wheat. If you avoid gluten, check the label, as some are made where wheat is handled. In Australia and New Zealand, look out for "wheaten cornflour", which is made from wheat, not maize.
How many carbs are in cornflour?
Cornflour is almost pure starch, and starch counts in full as carbohydrate. Here are the figures from the UK government's food composition data (CoFID), alongside other common thickeners and flours:
| Food | Carbs per 100g |
Carbs per 10g |
kcal per 100g |
|---|---|---|---|
| Cornflour | 92.0g | 9.2g | 354 |
| Arrowroot | 94.0g | 9.4g | 355 |
| Tapioca | 95.0g | 9.5g | 359 |
| Cornmeal, sifted | 73.1g | 7.3g | 368 |
| Plain white flour | 80.9g | 8.1g | 352 |
| Groovy Keto Xanthan Gum | 4.6g | 0.5g | 320 |
Source: CoFID 2021, foods 11-1045 (flour, corn, i.e. cornflour), 11-001 (arrowroot), 11-027 (tapioca, raw), 11-011 (cornmeal, sifted) and 11-886 (plain white flour). Xanthan gum figures are from our pack label. Carbohydrate excludes fibre, as on UK labels. Per-10g figures are our own calculations.
Cornflour also has just 0.6g protein and 0.7g fat per 100g, so nearly every gram is starch. That's what makes it such an effective thickener, and why it's carb-heavy.
Spoons vary, so here's the maths. King Arthur Baking puts a quarter of a US cup of cornstarch at 28g, which is about 7g per level tablespoon. That gives 7 × 0.92 = about 6.4g of carbs per level tablespoon. A rounded 10g spoonful has about 9.2g. If you're counting carbs, weigh it.
Say you thicken a gravy for four people with 15g of cornflour (about two level tablespoons). That's 15 × 0.92 = 13.8g of carbs in the pan, or about 3.5g per portion, before you count anything else in the gravy.
Why cornflour doesn't suit keto cooking
Keto and low-carb cooking keeps carbohydrate low, and cornflour is one of the most concentrated sources of carbohydrate in the cupboard, with more carbs per 100g than plain flour. It has almost no fibre either, so on a UK label there's nothing in it that isn't counted.
A small amount spread across a big pan isn't much per plate, as the gravy example shows. But it adds up quickly in recipes that rely on it: a cornflour-thickened custard, a fruit pie filling or a stir-fry sauce can easily use several tablespoons. The good news is that low-carb thickeners do the same job, often with a fraction of the amount.
Low-carb ways to thicken a sauce
There isn't one perfect swap for cornflour, but between them these methods cover gravies, cheese sauces, custards and dressings.
Xanthan gum
Xanthan gum is the closest like-for-like replacement. It's a very concentrated thickener, so a small pinch does what a spoonful of cornflour would. Unlike cornflour, it doesn't need to be boiled to thicken. It works in hot and cold liquids, so it's handy for dressings and cold sauces as well as gravy.
- Start small. Our pack guidance for sauces, gravies and dressings is a small pinch at a time. For custards and mousses, it suggests around a quarter of a teaspoon.
- Sprinkle and whisk. Scatter it over the surface while whisking, or blitz it in with a stick blender, so it doesn't clump.
- Give it a minute. It keeps thickening for a minute or two, so wait before you add more.
- Don't overdo it. Too much gives a slimy, gloopy texture. If that happens, loosen the sauce with more stock or cream.
Our xanthan gum guide covers what it is and how to use it in baking.
Mix the xanthan gum with a little oil, melted butter or the recipe's other dry ingredients before it goes in. Each grain gets coated, so it disperses evenly instead of forming jelly-like lumps.
Reduce the sauce
The simplest thickener is time. Simmer a gravy, pan sauce or tomato sauce uncovered and the water evaporates, concentrating the flavour as it thickens. Taste before adding salt, because the seasoning concentrates too.
Cream, cheese and butter
Double cream reduces into a thick, glossy sauce on its own. Grated cheese melts into it for a cheese sauce with no flour at all, which is how our keto cauliflower cheese sauce is made. For a pan sauce, take it off the heat and whisk in a few cubes of cold butter at the end to make it silky.
Egg yolks
Egg yolks thicken custards, curds and creamy sauces as they cook. Whisk the yolks, add a little of the hot liquid to them to warm them up, then pour everything back into the pan. Stir over a gentle heat until it coats the back of a spoon, and don't let it boil, or the eggs will scramble. Our keto custard is made this way with double cream and egg yolks, and uses xanthan gum instead of cornflour.
Why psyllium suits doughs better than sauces
Psyllium husk powder forms a gel with water, which makes it an excellent binder for keto bread, rolls and pizza bases. It can thicken a sauce, but it keeps thickening as it stands and can leave a slightly jelly-like, cloudy texture, so xanthan gum is usually the better choice for gravies and custards. If you're choosing between the two for baking, see how to use psyllium husk instead of xanthan gum.
Free delivery is on orders over £30.
Arrowroot, potato starch and tapioca
Arrowroot, potato starch (sometimes sold as potato flour) and tapioca starch are often suggested as cornflour substitutes, and for ordinary cooking they work well. They aren't low-carb, though. They're all starches, so they have much the same carbs as cornflour: CoFID gives 94.0g per 100g for arrowroot and 95.0g for tapioca.
Each behaves a little differently:
- Arrowroot thickens at a lower temperature and gives a clear, glossy finish, which suits fruit sauces and glazes. It can turn slimy in dairy-based sauces, and it thins if cooked for too long.
- Potato starch thickens strongly and quickly. Add it near the end of cooking and don't boil it hard for long.
- Tapioca starch gives a glossy, slightly stretchy texture and is popular in fruit pie fillings.
So if you've run out of cornflour, any of these will do the job in similar amounts. If you're trying to cut carbs, they won't help, and xanthan gum or one of the other methods above is the better choice.
For anyone in the house not cooking low-carb: mix cornflour with a little cold water until smooth, stir it into the hot liquid, then bring it to the boil and simmer for a minute. It only reaches full thickness once it boils, and the short simmer cooks out the raw, starchy taste.
Frequently asked questions
Can I use cornflour instead of cornstarch?
Yes. UK cornflour and US cornstarch are the same product, a fine white starch made from maize, so you can use exactly the same amount. If a US recipe asks for 2 tablespoons of cornstarch, use 2 tablespoons of cornflour. It thickens sauces, gravies, custards and pie fillings in the same way.
Is cornflour the same as corn flour in the US?
No. In the US, corn flour (two words) means whole maize kernels ground into a fine yellow flour, which is closer to UK maize flour or fine cornmeal. It doesn't thicken like pure starch, so don't use it in place of cornstarch. When a US recipe says cornstarch, use UK cornflour.
How many carbs are in a tablespoon of cornflour?
About 6.4g in a level tablespoon. CoFID gives cornflour 92.0g of carbohydrate per 100g, with almost no fibre, and a level tablespoon weighs about 7g. A rounded 10g spoonful has about 9.2g. Spoons vary a lot, so weigh it if you're counting carbs.
What can I use instead of cornflour on keto?
Xanthan gum is the closest swap, because a small pinch thickens a sauce without adding many carbs. You can also reduce a sauce by simmering it, enrich it with double cream, cheese or butter, or thicken a custard with egg yolks. Arrowroot, potato starch and tapioca are starches, so they don't cut the carbs.
How much xanthan gum replaces cornflour?
There's no exact conversion, because xanthan gum is far stronger. Our pack guidance for sauces and gravies is a small pinch at a time: sprinkle it in while whisking, wait a minute, then add more only if needed. For custards and mousses it suggests around a quarter of a teaspoon. Too much makes a sauce slimy.
Sources
- GOV.UK / Public Health England. Composition of Foods Integrated Dataset (CoFID) 2021. Carbohydrate, protein, fat and energy per 100g for flour, corn (11-1045), custard powder (11-1138), arrowroot (11-001), tapioca, raw (11-027), cornmeal, sifted (11-011) and plain white flour (11-886). Per-tablespoon and per-portion figures are our own calculations.
- King Arthur Baking. Ingredient weight chart: cornstarch 28g per quarter US cup.
- Food Standards Agency (GOV.UK). Allergen guidance for food businesses: cereals containing gluten as one of the 14 allergens.
- Groovy Keto product pages: Xanthan Gum (150g) and Psyllium Husk Powder: ingredients, nutrition per 100g and usage guidance.
