You can use kosher salt instead of flaky sea salt at a ratio of 1:1 by volume. Salt swaps are not about the saltiness of the salt — all salt is sodium chloride — they are about the size and shape of the crystals, and that is where most people go wrong. Salts differ by crystal size, so swap by weight, not by volume — kosher salt is far lighter per cup than table salt. A teaspoon of fine table salt packs far more salt into the spoon than a teaspoon of big, hollow kosher flakes, so a cup-for-cup swap can easily double the salt or halve it. The ratio above is the sourced ratio for this pair, and the table below scales it to the amounts recipes actually call for.
This matters more than it sounds. Salt is the one ingredient in almost every recipe, and it is the one where a small measuring error is immediately obvious: too little and the dish tastes flat, too much and it is inedible. That is why this guide spends time on weighing. A kitchen scale removes the whole problem — the same weight of any salt is the same amount of salt, whatever the crystal size. If you cook with more than one kind of salt, a scale is the single best purchase you can make, and it costs less than a bag of good flaky salt.
The ratio, in a table
| Flaky sea salt called for | Kosher salt |
|---|---|
| 1/2 tsp | 1/2 tsp |
| 1 tsp | 1 tsp |
| 1 tbsp | 1 tbsp |
| 1/4 cup | 1/4 cup |
The numbers in the table are the ratio 1:1 by volume scaled up and down. All amounts in this guide are approximate, and the ratio comes from CookScale's substitution data rather than from a single brand's packaging. If the recipe matters — a cake for a celebration, a batch you are selling, or anything where a small error shows — weigh the ingredients on a kitchen scale and taste as you go. If you are in doubt, undershoot: add two-thirds of the salt, taste, and add the rest. You can always add more salt at the end of cooking, but you cannot take it out, and an over-salted pot is a much bigger problem than an under-salted one.
Worked examples
Example 1: A steak, finished with kosher salt
A steak recipe calls for 1 tablespoon of flaky sea salt to finish the meat. Use 1 tablespoon of kosher salt instead, and the steak will be seasoned the same — the ratio is 1:1 by volume. The kosher salt will not give quite the same delicate crunch as the flakes, because its crystals are denser and less hollow, but it will still give a pleasant crunch and a burst of salt. Scatter it over the rested steak just before serving, so it stays crunchy rather than dissolving into the meat juices.
Example 2: A focaccia that needs its salty top
A focaccia recipe calls for 1 tablespoon of flaky sea salt pressed into the dimples with olive oil. Use 1 tablespoon of kosher salt instead, and the bread will have the same salty, crackling top. Kosher salt is a little denser than flaky salt, so the crust will be slightly less delicate, but the effect is the same: a salty crunch that contrasts with the soft bread underneath. Press the salt into the dimples so it sticks, and bake until the top is golden.
Example 3: A chocolate brownie with a salted top
A brownie recipe calls for 1 teaspoon of flaky sea salt scattered over the top before baking. Use 1 teaspoon of kosher salt instead, and the brownies will have the same sweet-salty contrast. The kosher crystals are a little heavier than flakes, so they will sit slightly deeper in the batter, but they will still be visible on the surface and they will still give the burst of salt that makes a salted brownie work. Let the brownies cool completely before cutting, so the salt stays on top.
What changes in the result
The flavour change is none: both are sea salt, both are sodium chloride, and both dissolve the same way. What changes is the texture, and only slightly: flaky salt has delicate, hollow crystals that shatter on the tongue, while kosher salt has denser, flatter crystals that crunch a little more firmly. On top of a steak, a focaccia or a brownie, the difference is noticeable if you are looking for it, and invisible if you are not. Inside a dish, there is no difference at all, because both dissolve completely. This is one of the easiest salt swaps, because the ratio is 1:1 by volume and the result is the same in almost every use.
Texture changes too, in ways that have nothing to do with saltiness. Fine salt dissolves quickly and disappears into a sauce or a dough; coarse flakes dissolve slowly and can leave crunchy pockets if they are added late. Flaky salt sprinkled on top of a finished dish stays crunchy and gives little bursts of salt — that is its whole appeal. Kosher salt is the cook's favourite for seasoning by hand because the big crystals are easy to pinch and scatter evenly, and you can see where it has landed. None of this changes the flavour of the salt itself, but it changes how the dish eats, and that is what the cook is really choosing.
When not to substitute
Do not swap salts cup-for-cup; Diamond Crystal kosher salt is about half the weight of table salt per cup. Do not use table salt as the substitute here — it has no crunch at all, and a finishing salt needs crunch. Kosher salt is the right substitute because it is the only common salt with crystals big enough to give a similar effect. And do not grind the kosher salt: grinding destroys the crystals, which is the entire point of a finishing salt.
There are also jobs where one salt is simply the wrong tool. Do not use a coarse salt in a recipe where it has to dissolve quickly and completely — a smooth sauce, a meringue, a brine that needs to be exact — unless you give it time and stirring. Do not use a flavoured salt, like the celery salt in this guide's family, where the extra flavour would clash: it is a seasoning in its own right, not a neutral stand-in. And do not use an expensive finishing salt inside a dough or a stew, where its crunch and its delicate flavour disappear entirely. Save the good salt for the top of the dish, where you can taste it.
Practical guidance
Keep one salt as your everyday cooking salt and learn its measure by feel — most cooks use kosher salt for that, because it is easy to pinch and forgiving to scatter. Keep a small dish of flaky salt by the stove for finishing, and keep table salt for baking, where its fine crystals dissolve evenly and its exact measure matters. Label your containers, because kosher salt and table salt look similar in a jar and they are not interchangeable by the spoonful. When a recipe just says 'salt' with no kind given, it usually means table salt in older books and kosher salt in newer ones — if the result tastes under-salted, the recipe probably meant the finer salt, and if it tastes over-salted, it probably meant the coarser one. Taste as you cook, salt in stages rather than all at once, and remember that sauces and soups concentrate as they reduce, so the salt you add at the start tastes stronger by the end.
Kosher salt is the workhorse finishing salt when flaky salt is not in the cupboard: it is cheap, it is always available, and it gives a good crunch. Keep a small bowl of it by the stove for seasoning by hand, and keep the flaky salt for the occasions when the delicate crunch is worth the price. Both should be stored dry and sealed, because they absorb damp from the air.
Frequently asked questions
Is kosher salt the same as flaky sea salt?
No, but they are close. Flaky sea salt is evaporated slowly so the crystals grow into delicate, hollow flakes; kosher salt is made by a different process and its crystals are denser and flatter. Both are large-crystal salts, both are used for finishing, and they swap 1:1 by volume. The difference is texture: flakes are more delicate, kosher salt is a little crunchier.
Can I use kosher salt on top of a finished dish?
Yes — that is one of its best uses. Kosher salt scattered over a steak, a focaccia or a brownie just before serving gives a salty crunch that fine salt cannot give. It is not as delicate as flaky salt, but it is far better than table salt, which has no crunch at all. Use it when the flaky salt jar is empty, and nobody at the table will complain.
Can I just swap salts 1:1 by volume?
Only if the two salts have similar crystal sizes. Fine sea salt and table salt are close enough for most cooking, and the ratio for this pair is 1:1 by volume. But kosher salt and flaky salt are much lighter per spoonful, so a 1:1 volume swap under-salts the dish — sometimes by half. The safe rule is to swap by weight: the same weight of any salt is the same amount of salt, whatever it looks like.
Why do recipes specify a brand of kosher salt?
Because the two big brands are different densities. Diamond Crystal kosher salt is light and hollow, Morton is denser and heavier, so a teaspoon of one is not a teaspoon of the other. A recipe written for Diamond Crystal needs about one and a half teaspoons per teaspoon of table salt, while Morton needs about one and a quarter. If a recipe does not say which brand, Diamond Crystal is the usual assumption in American recipes.
Does the kind of salt change the flavour?
Barely, once it is dissolved. All salt is sodium chloride, and dissolved in a soup or a dough the differences are tiny. What changes is texture — flakes stay crunchy on top of a dish — and the trace minerals in some sea salts, which can add a very faint bitterness or sweetness that most people cannot detect in a finished dish. Choose salt for its crystal size and how you use it, not for a flavour difference you probably cannot taste.