Salmon in the Oven: How Long to Cook It

The short version: a standard salmon fillet (about 2cm/150g) bakes in 12 to 15 minutes at 200C/400F, but the only number that matters is thickness, not weight or time written on a recipe card. Measure the fillet at its thickest point, allow roughly 4 to 5 minutes per centimetre, and pull it out when it hits 50 to 52C in the centre for a moist result or 58C if you want it fully opaque right through. Everything else, including the oven temperature you pick, is really just a way to control how forgiving that window is.

Why "12 to 15 minutes" is almost useless advice on its own

I've lost count of the recipe cards that say "bake salmon for 12 to 15 minutes" as if every fillet that lands on a chopping board is the same size. It isn't. A thin tail-end fillet from a side of salmon can be 1.5cm thick. A thick centre-cut fillet can be 3.5cm. Cook both for the same 15 minutes at the same temperature and the thin one is dry cardboard while the thick one is still raw in the middle.

The uncomfortable bit nobody wants to say out loud: most salmon failures aren't a timing problem, they're a thickness problem that a timer can't fix. If you want consistent results, you need a ruler more than you need a recipe.

The actual rule that works every time

• Measure the fillet at its thickest point with a ruler or just eyeball it against your finger (a finger is roughly 1.5 to 2cm).
• At 200C/400F fan oven, allow 4 to 5 minutes per centimetre of thickness.
• Start checking 3 minutes before your calculated time is up.
• Pull it when the thickest part flakes gently with a fork and the centre is still slightly translucent, or use a thermometer and take it out at 50 to 52C (it will climb a few more degrees as it rests).

A worked example: say you're cooking dinner for four

Say you're cooking four salmon fillets for dinner tonight, two of them thick centre cuts at 3cm and two thinner tail pieces at 1.8cm, all from the same side of salmon because that's what the supermarket had reduced that day.

• Preheat the oven to 200C/400F fan, or 220C/425F conventional (conventional ovens run cooler without a fan, so push the temperature up by 20 degrees to compensate).
• Line a tray with foil or baking paper, skin-side down if the skin is on, drizzle with a tablespoon of oil, season with salt and pepper.
• Put the thicker fillets in first and give them a 4 minute head start, then add the thinner ones to the same tray.
• Thick fillets (3cm): roughly 12 to 15 minutes total.
• Thin fillets (1.8cm): roughly 8 to 9 minutes total.
• Check the thick ones at the 12 minute mark with a fork at the thickest point. If it flakes and still has a faint pink sheen in the centre, it's done. If it resists, give it another 2 minutes and check again.
• Rest everything on the tray for 2 minutes before serving. The residual heat finishes the job and the fish firms up.

That staggered start is the whole trick. Nobody tells you that one tray of mixed sizes doesn't need two separate cooking sessions, just two separate entry times.

Oven temperature changes the result, not just the clock

There are really three sensible approaches, and which one you pick depends on what you want out of the fish, not just how fast you want dinner on the table.

• High heat, short time (220 to 230C, 8 to 12 minutes): gives a slightly crisp top and a fast cook, good for weeknights when you're also juggling rice or potatoes in the same oven. Easier to overshoot if you walk away.
• Moderate heat (180 to 200C, 12 to 18 minutes): the safest middle ground for most home cooks, forgiving by a minute or two either side, this is the one I'd default to for a normal Tuesday fillet.
• Low and slow (120 to 140C, 20 to 25 minutes): produces an almost custard-like texture, popular with chefs doing restaurant plating, but it's slower than most people have patience for on a school night and needs a thermometer to avoid guessing.

If you're stuck for what else to put alongside it, my dinner ideas page has quick sides that cook in roughly the same window, so you're not juggling three timers at once.

Skin on or off changes your timing too

Skin-on fillets cook slightly differently because the skin acts as a barrier between the heat and the flesh on that side. Put skin-side down on the tray and you get a bit of protection against overcooking the bottom, plus the skin crisps up if you're baking at the higher end of the temperature range. Skinless fillets cook a touch faster, maybe a minute less than the equivalent skin-on thickness, because there's nothing slowing the heat transfer.

Frozen fillets that haven't been defrosted need roughly 50% longer than fresh, and I'd always rather defrost overnight in the fridge than guess at oven timing with ice still in the middle. If you're short on time, a cold water bath for 20 to 30 minutes in a sealed bag gets a fillet defrosted safely without starting to cook the edges, which a microwave defrost setting can easily do by accident.

Foil, parchment, or nothing at all

Wrapping salmon in a foil parcel traps steam and effectively poaches the fish in its own moisture, which is the most forgiving method for anyone nervous about drying it out. It adds roughly 2 to 3 minutes to the cook time because the steam has to build up first, but it buys you a wider safe window.

Baking uncovered on parchment gives you a drier heat and a slightly firmer texture, with less margin for error if you're distracted by something else in the kitchen. Baking uncovered directly on foil with oil gets you closer to roasting, with a bit of colour on top if your oven runs hot.

None of these methods are wrong. They're just different tools for different tolerance levels, a bit like choosing between a grill pan and an air fryer when you want speed over fuss, both get you to cooked fish, they just get you there with different textures and different margins for error.

How to tell it's done without cutting it in half

Cutting into the middle to check is the thing most people do, and it's the reason the fish ends up dry, because that cut lets steam and juice escape right before serving. Instead:

• Press gently at the thickest point with a fork. If it separates into flakes with slight resistance, it's ready.
• Look at the side of the fillet rather than the top. The colour change from translucent to opaque travels up from the outside in, so a thin band of translucency in the very centre at the thickest point means it's just about right and will finish during resting.
• If you cook fish regularly, a cheap instant-read thermometer is worth the money. 50C is medium, 58C is well done, and anything over 63C is firmly into dry territory whatever the recipe card promised you.

Food safety guidance from bodies like the US Food and Drug Administration recommends cooking fish to an internal temperature of 63C (145F) to be safe for everyone, including people who are pregnant or immunocompromised. If you or anyone you're feeding falls into that category, go with that number rather than the chef-preferred lower temperatures in this post, and speak to your GP or doctor if you have specific dietary concerns around food safety.

The mistakes that ruin it most often

• Cooking straight from the fridge. A cold fillet takes longer to come up to temperature and cooks unevenly. Give it 10 minutes at room temperature before it goes in.
• Opening the oven door repeatedly. Every check drops the oven temperature and adds time you haven't accounted for.
• Trusting the weight on the packet instead of measuring thickness. Two 150g fillets can be completely different shapes, one long and thin, one short and thick, and they will not cook in the same time.
• Not resting it. Two minutes off the heat lets the residual warmth finish the centre gently instead of you overcooking it trying to get there in the oven.

If you take nothing else from this, take the ruler point. Weight tells you how much you're eating, thickness tells you how long to cook it, and treating those as the same thing is where most kitchen disasters with salmon start.

I have written more around this on the site: Best Air Fryer (2026): Types, Brands and What to Look For, What to Make for Dinner Tonight: Easy Ideas for Any Night.

Frequently asked questions

How long do you cook salmon in the oven at 180C?

At 180C a standard 2cm fillet takes roughly 15 to 18 minutes. Thicker fillets of 3cm or more can take up to 22 minutes, so check at the 15 minute mark with a fork and add time in small increments rather than guessing a long cook upfront.

Do you need to cover salmon with foil in the oven?

No, it isn't necessary, but wrapping it loosely in a foil parcel traps steam and makes the fish harder to dry out, which is useful if you're not confident judging doneness yet. Uncovered baking gives a firmer texture and a bit more colour on top.

Is it better to bake salmon at a high or low temperature?

High heat (220 to 230C) gives a faster cook with a slight crisp on top but less room for error. Lower heat (120 to 140C) gives a softer, almost custard-like texture but takes 20 to 25 minutes and really needs a thermometer. Moderate heat around 190 to 200C is the easiest starting point for most home cooks.

How do you know when salmon is cooked without a thermometer?

Press gently at the thickest part with a fork. It should flake apart with a little resistance, and the very centre should show only a thin band of translucency, which finishes cooking during a 2 minute rest off the heat.