Butterfly Cut Fish: How to Butterfly and Split a Whole Fish
A butterfly cut fish has had its backbone and ribs removed while the two fillets stay joined, so the fish opens flat into one bone-free piece. Run a sharp fillet knife along each side of the spine, then snip the bone free with kitchen shears.
Butterflying a fish, also called splitting it, is a close cousin of filleting a fish — the difference is that you finish with one connected, flat fillet instead of two separate ones. It is the cut you want for stuffing a whole fish, grilling it flat, or cooking mackerel, trout, branzino and sardines evenly without diners picking out bones. Here is how to do it cleanly, updated for 2026.
What is a butterfly cut on a fish?
A butterfly cut removes the spine and rib bones from a gutted fish while keeping the two sides attached, either along the back or along the belly. Opened out, the fish resembles a butterfly: flat, even in thickness, skin on one side and flesh on the other. Because the fish lies flat, it cooks fast and evenly, and because the bones come out before it ever meets heat, everyone at the table eats without hunting for pin bones.
So when a recipe or a fishmonger says a fish is butterflied, it means exactly this: deboned, still in one piece, ready to open like a book. It is not the same as cutting a fish in half. Cutting a fish in half gives you two pieces and leaves the bones where they were; butterflying gives you one piece and takes the bones out.
Is splitting a fish the same as butterflying it?
In practice, yes. "Split fish" and "butterflied fish" describe the same result, and you will hear both words in the same kitchen. Splitting is the older term, still standard in smokehouses and on fishing boats, where a split mackerel or a split trout means one opened out flat over the fire. Butterfly is the restaurant word for it, and the one most recipes now use.
The only time the two words part company is on a whole round fish that has been opened but not deboned — some cooks will still call that split. If you are buying rather than cutting, the question worth asking is not which word the counter uses but whether the backbone has actually come out.
What you need
A flexible, razor-sharp fillet knife does the fine work along the bones. Ours is the 7" Bushcraft Fillet Knife, hand sharpened and oiled before it ships like every blade we forge. Add kitchen shears for the spine, tweezers for pin bones, and a cutting board with a damp towel underneath so nothing slides. A cut-resistant glove on your guide hand is cheap insurance.
Flex is the specification that matters. A blade that bends will follow the curve of a rib cage and leave the bone clean; a stiff blade cuts a straight line through a curved fish and takes flesh with it. If you only own a chef knife, a 5" or 6" utility blade such as the Feather Forge 6" Utility is a far better stand-in than an 8" chef knife, simply because the tip stays under control.
How to butterfly a fish, step by step
1. Start with a gutted, scaled fish
Scales and guts must go first — your fishmonger will do this in seconds if you ask. Remove the gills, then rinse and dry the cavity so your knife will not slip.
2. Extend the belly opening
Lay the fish on its side and run the tip of your fillet knife from the gutting cut down to the tail, opening the belly fully without piercing through the back skin.
3. Free the ribs on the first side
Working from the cavity, slide the blade flat along the rib cage and let the bones guide the knife. Use long, shallow strokes — you are separating flesh from bone, not sawing.
4. Free the second side
Turn the fish and repeat on the other rib cage, keeping the back intact so the two sides stay joined.
5. Cut along the spine
Angle the knife along each side of the backbone from the head end to the tail, releasing it from the flesh while leaving the skin along the back uncut.
6. Remove the backbone with shears
Snip the spine at the head and tail ends with kitchen shears and lift it out in one piece, ribs and all.
7. Pull the pin bones and open it flat
Run a fingertip against the grain of the flesh to find stray pin bones and pull them with tweezers. Open the fish out flat — it is ready to stuff, grill or pan-roast.
Back cut or belly cut? Butterfly vs reverse butterfly
The seven steps above describe the belly cut, which is the standard butterfly: you enter through the gutting cut, so the fish opens belly-first and the unbroken skin runs along the spine. That is what most recipes assume, and it is the easier of the two because the cavity is already open.
A reverse butterfly, or back cut, goes in from the top instead. You cut down either side of the dorsal fin, lift the backbone out through the back, and leave the belly skin holding the two halves together. It takes a steadier hand, but it is the better cut for stuffing, because the belly seam forms a natural pouch that holds herbs, citrus and butter instead of letting them slide out. Smokehouses tend to prefer it too, since the thicker back flesh faces the heat.
Either way the tool is the same and so is the finish: a flat, deboned fish. Choose the belly cut for speed and the back cut when the filling matters.
How to butterfly a trout, branzino, mackerel or snapper
The method does not change from fish to fish, but the feel of it does, and knowing what to expect is most of the skill.
Trout is the one to learn on. The rib bones are soft, the flesh is forgiving, and the pin bones lift out cleanly. A whole butterflied trout is also about the right thickness to cook through before the skin burns.
Branzino has a firmer frame and a smaller cavity, so work slowly at step 3 and keep the blade pressed against the ribs rather than into the flesh. It rewards the effort: butterflied branzino is the classic whole-fish-on-the-grill plate.
Mackerel is oily and soft, which means a dull knife will tear it. This is the fish that exposes a blunt blade fastest. Split mackerel over coals, skin down, is one of the best arguments for learning the cut at all.
Snapper and other larger round fish have stiffer ribs and heavier spines — use the shears earlier and more often rather than forcing the knife. Perch and other small panfish are fiddly but follow the same order of operations.
Flatfish such as sole and plaice are the exception. Their skeleton runs flat through the middle rather than round the body, so they are filleted, not butterflied.
How to butterfly a fish for grilling or frying
Butterflying exists mostly because of these two jobs. For the grill, leave the skin on and the fish whole, oil the skin rather than the grate, and cook skin-side down for most of the time — a flat fish of even thickness will be done in minutes and needs turning only once, if at all. The flat shape is what stops the tail overcooking while the shoulder is still raw.
For frying, dry the flesh thoroughly before it meets flour or batter, and go in flesh-side down first so the exposed side sets before the skin crisps. A butterflied fish fries in a single pan without being cut into portions, which is exactly the point.
In both cases the bones are gone before cooking, so the fish can be served whole and eaten straight off the plate.
Butterfly cut vs filleting: which should you use?
Fillet when you want individual portions or skinless pieces. Butterfly when you want the whole fish cooked as one — stuffed, flattened on a grill, or served dramatically whole. Butterflying also wastes less meat, since nothing is trimmed away from the bone twice.
If you are still choosing a blade for either job, our utility and fillet knives are the shapes built for it, and the fillet guide covers the two-piece cut in the same detail.
Common questions
What does it mean if a fish is butterflied? It means the backbone and ribs have been taken out while the two fillets stay attached, so the fish opens flat into one piece. Butterflied fish is ready to cook and free of the main bones.
Can you butterfly a fish with the skin on? Yes — the skin is what holds the two sides together, so it has to stay on. It also crisps beautifully and keeps the flesh moist.
Which fish are best for butterflying? Round fish with soft rib bones: trout, mackerel, branzino, snapper, sardines and small salmon. Flatfish such as sole are better filleted.
Do I need a special knife? You need a thin, flexible, genuinely sharp blade — a stiff chef knife will tear the delicate flesh. A dedicated fillet knife pays for itself the first time you break down a catch.
Shop the range
Every blade from The Cooking Guild is hand sharpened and oiled before it ships — the sharpest blades you will ever use, or your money back. Try the Bushcraft Fillet Knife, browse the full utility and fillet knife collection, or start with a hand-forged chef knife. Every knife comes with a 99-day home trial and a free lifetime guarantee.
Keep reading: Best Knives for Outdoor Cooking · Outdoor Knife Care: Rust, Edge and Storage · How to Fillet a Fish · 6 Basic Knife Safety Rules · Essential Knives for Outdoor Cooks
