Fish Cooking Time Calculator
This is the general-purpose method for any fillet, steak or whole fish. Choose the cut and how you are cooking it, then measure the thickness or weigh the whole fish.
A tail-end fillet is much thinner than a middle-cut piece, so measure the thick end.
Answer
14–18 minutes at 200°C
What to do
- 1Heat the oven to 200°C.
- 2Cook for 14 to 18 minutes.
- 3Bake uncovered on a lined tray. The fish is done when it has turned opaque and flakes apart with gentle pressure.
- 4Fish keeps cooking off the heat, so take it out as soon as it flakes rather than waiting for it to look well done.
How to check it is done
Bake uncovered on a lined tray. The fish is done when it has turned opaque and flakes apart with gentle pressure.
Next step
Food safety
- Official UK guidance checks fish by sight rather than by a single temperature: the flesh should turn opaque and flake apart easily with a fork. Prawns, scallops, crab and lobster should be firm and opaque, and mussels, clams and oysters should have opened, throw away any that stay shut.
- Cooking times are a guide only. Ovens, joints and starting temperatures vary, so always check the food is cooked before serving rather than relying on the clock.
Source: Food Standards Agency, Cooking your food: cooking fish and seafood (GOV.UK) · Reviewed 2026-09-11 · Guidance version 2.0.0
Source: Food Standards Agency, Cooking your food: cooking fish and seafood (GOV.UK) · Reviewed 2026-09-11 · Guidance version 2.0.0
Reference and detail
One method for any fish
This calculator covers the by-thickness and by-weight method that works for any species, sea bass, plaice, pollock, trout and anything else you cannot find a dedicated page for. If you are cooking salmon, cod, haddock or prawns specifically, their own pages give timings and checks tailored to that fish.
Fish cooks by thickness, not weight
A 2cm fillet takes about the same time whether it weighs 150g or 400g. Weight only becomes the better guide for a whole fish, where heat has to travel past the bone and into the cavity. That is why this calculator asks for thickness for fillets and weight for a whole fish.
Knowing when to stop
Official UK guidance checks fish by sight rather than a single temperature: cooked fish turns from glassy to opaque and the flakes separate when you press them. For a whole fish, the flesh should come away from the backbone cleanly at the thickest point behind the head. Fish carries on cooking off the heat, so stop just before you think it is ready.
Cooking a whole fish
Slash the skin two or three times on each side so heat reaches the middle, and fill the cavity with lemon, herbs and a little butter. Bake it on a tray it can be served from, a cooked whole fish will not survive being moved twice.
Questions and answers
Questions about cooking fish
How can I tell if fish is cooked without a thermometer?
Press the thickest part with a fork. Cooked fish turns from glassy to opaque and separates into flakes; if it still looks translucent and resists the fork, it needs longer.
For a whole fish, check where the flesh meets the backbone behind the head. It should lift away cleanly rather than clinging.
Should I cook fish by weight or by thickness?
Use thickness for fillets and steaks, and weight only for a whole fish. A thin fillet and a thick one of the same weight cook in very different times, because heat only has to travel through the depth of the flesh, not across it.
Enter the thickness or weight above and choose the method for a time to start checking at.
Can I cook fish from frozen?
Thin fillets can go into the oven straight from frozen. Allow extra time and check the centre is piping hot before serving. Thicker fillets, steaks and whole fish are better defrosted in the fridge first, so the outside does not overcook while the middle catches up.
Why did my fish break apart when I turned it?
Fish flesh is delicate and separates along natural seams once it is cooked, so it is easily damaged by turning it too often or too roughly. Use a fish slice, turn it only once, and make sure it has released from the pan before you try to move it.
Is it safe to eat fish slightly pink in the middle?
Fish should be cooked until it is opaque all the way through and flakes apart easily with a fork; it is checked by sight rather than a core temperature, and is not treated the same as beef or lamb, which can be served rare. If you are unsure, give it another minute or two and check again.
Food safety
Official UK guidance checks fish by sight rather than by a single temperature: the flesh should turn opaque and flake apart easily with a fork. Prawns, scallops, crab and lobster should be firm and opaque, and mussels, clams and oysters should have opened, throw away any that stay shut.
Source: Food Standards Agency, Cooking your food: cooking fish and seafood (GOV.UK) · Reviewed 2026-09-11 · Guidance version 2.0.0
Safety guidance reviewed against Food Standards Agency sources on 11 September 2026. How we calculate cooking times and safety guidance.