Kitchen Extraction Rate: Sizing & Ducting Guide
At Mayfair Kitchens, we know extraction is rarely the part of a new kitchen anyone looks forward to discussing. It is also one of the details that decides whether you enjoy the room every day.
As a starting point, your kitchen extraction rate should be around 10 times the volume of the room every hour. Measure the length, width, and height, multiply them together, then multiply that figure by 10. The answer, in cubic metres per hour, is the rate to work from.
The appliance is only half of it. A powerful hood pushed through a narrow duct with three bends in it will move less air, and make far more noise doing so, than a modest hood on a short, straight run. Whether you are updating a Victorian terrace in Chester or creating an open-plan extension on the Wirral, we plan the route alongside the appliance rather than after it.
How to Work Out Your Kitchen Extraction Rate
Take a kitchen measuring 5m by 4m, with a ceiling height of 2.5m. That gives a room volume of 50m³. Multiplied by 10, you need an extractor rated at roughly 500m³/h.
The calculation matters because it ties the appliance to your actual room. Kitchen extractor size is too often decided by the width of the hob, or simply by what suited the look of the space, and neither says much about how much air the room needs moved.
Width still counts. Your extractor should be at least as wide as the hob, and ideally 100mm wider on each side. Steam does not rise in a neat column. It drifts, and a hood that stops at the edge of the hob lets a good deal of it past.
Kitchen ventilation is also a regulatory matter. Building Regulations have required extract ventilation in kitchens since April 2006, and the current figures sit in Approved Document F:
- 30 l/s for intermittent extraction next to the hob
- 60 l/s for intermittent extraction elsewhere in the room
- 13 l/s minimum for continuous extraction
Check the current guidance and your appliance specification for your own project, as manufacturers set their own installation requirements on top.
Ducted or Recirculating Extraction?
A ducted extractor sends cooking air outside. A recirculating one filters it and returns it to the room. Where a sensible route to an external wall exists, our advice is almost always to duct it.
The reason is moisture. Grease and charcoal filters handle a good deal of odour and airborne fat, but no filter removes water vapour. Recirculated air comes back into the kitchen carrying everything the steam was holding, and over the years that shows on paintwork, in cabinetry, and on cooler surfaces near the hob.
Recirculation still earns its place. Apartments, internal kitchens, period properties where the fabric cannot be cut into, and any project where reaching an external wall would mean five metres of duct and four bends. In those cases, a recirculating system on a short run serves you better than a ducted one working its way across the building.
Two practical differences: recirculating systems need charcoal filters replaced every 6 to 12 months, whereas ducted ones generally do not, and a recirculating unit can sit almost anywhere, whereas a ducted one goes where the route allows.
Either way, decide at the design stage. Retrofitting a duct route through finished cabinetry is expensive and rarely tidy.
Why the Ducting Matters More Than the Hood
An extractor can only move air as fast as the duct allows. Every reduction in diameter, every extra metre, and every bend adds resistance, which shows up as weaker extraction and more noise.
This is where money gets wasted. Someone has a noisy, ineffective extractor, replaces it with something more powerful, and the new appliance disappoints in the same way. The hood was never the problem.
Duct diameter. 150mm is standard for most modern extraction. Drop to 125mm, and you are pushing the same volume of air through a noticeably smaller opening, raising both resistance and noise. Ducts get reduced because a smaller one is easier to hide, and we would encourage you to resist that. Cabinetry should be built around the duct your appliance needs. A route passing through a tall unit, ceiling void, or bulkhead is far simpler to plan through our bespoke kitchen design service before anything is manufactured.
Length of run. The shortest sensible route outside wins. Each bend costs you roughly the same as another metre of straight duct, so two or three tight turns will change an extractor’s performance entirely even though the appliance is identical. We work the route out during the technical survey stage, while walls and units can still move around it.
Rigid rather than flexible. A rigid duct has a smooth bore, so air moves cleanly and quietly. A flexible duct is ridged inside, and those ridges churn the airflow into turbulence you will hear as a rushing sound above the lowest setting. Short flexible connections where alignment is awkward are fine. Long flexible runs, chosen because they were quicker to fit, are not.
Choosing the Right Type of Extractor
The right extractor depends on your hob position, ceiling construction, duct route, and how visible you want the appliance to be.
Chimney extractors sit above the hob in full view and give the most direct route out, particularly where the hob is on an external wall. Extractor hood height should be 650 to 750mm above induction and electric hobs, and at least 750mm above gas, though manufacturer figures always take precedence.
Integrated extractors disappear into the cabinetry, which suits kitchens where an unbroken run of units matters more than a statement appliance. Concealing one does not remove the ducting requirement, so allow room within or above the cabinet for the unit and the full duct diameter.
Ceiling extractors leave the space above the hob completely clear, which works beautifully in open-plan rooms. Sitting further from the cooking surface, they need careful sizing, and the ceiling void must accommodate both the unit and its route out.
Downdraft systems draw vapour sideways or downwards, so they suit kitchens where open sightlines matter. The cost is underneath, where motors and ducting take space that would otherwise be drawers.
Venting hobs combine cooking surface and extraction in one appliance, giving a very clean result on an island where a suspended hood would feel intrusive. The air still has to go somewhere, so settle the duct route and the storage you lose as part of the island design.
Extraction Over a Kitchen Island
You can extract over an island using a ceiling extractor, suspended hood, downdraft system, or venting hob. Which suits depends on your ceiling construction, the route available, and how much cabinet space you can give up.
An overhead hood captures best, sitting directly above the hob, but becomes a significant object in an open room. Ceiling extraction keeps the sightline clean at the cost of void space above. Downdraft systems and venting hobs keep both ceiling and eye-line clear, taking their space from your drawers instead.
Settle this alongside the kitchen island dimensions rather than once the island is drawn, as an extractor introduced late tends to eat the storage the island was designed to provide. Lighting needs deciding at the same moment, since pendants, ceiling extraction, and downlights all compete for the same area of ceiling. Coordinating it with the lighting scheme early is far easier than reconciling them after the first fix.
Noise, Filters, and Maintenance
Extractor noise comes from the appliance and the duct together. Boost settings commonly sit around 50 to 55 dB(A), though models vary widely, and a well-designed route does more for the sound of your kitchen than a marginally better rating on paper.
Compare figures across the whole speed range rather than peak extraction alone. Most everyday cooking does not need full power, and an extractor that only works properly on boost is one people quietly stop switching on.
Grease filters need cleaning at whatever interval your manufacturer recommends, since a clogged filter restricts airflow and makes the motor work harder for less result. One last thing worth raising at installation is access: filters should slide out easily, and anything needing servicing should not end up boxed in behind a permanent panel.
Frequently Asked Questions
What kitchen extraction rate do I need?
Your kitchen extraction rate should be roughly 10 times the room volume per hour. Multiply the volume in cubic metres by 10, so a 50m³ kitchen needs approximately 500m³/h as a starting figure, adjusted for the appliance specification and duct route.
Do Building Regulations require an extractor hood?
They require extract ventilation in kitchens, not a particular style of hood. What matters is that the system meets the ventilation requirement, so check the current Approved Document F guidance for your project.
Is a ducted or recirculating extractor better?
Ducted, where a practical route outside exists, because it removes moisture as well as odour. Recirculating systems are the sensible answer where external ducting would mean a long or heavily bent run.
How high should an extractor be above the hob?
Around 650 to 750mm above induction and electric hobs, and at least 750mm above gas. Always follow the hob and extractor manufacturers’ stated distances.
Why is my extractor so noisy?
Usually, the ducting rather than the appliance. A duct that is too narrow, runs too far, turns too often, or uses long lengths of flexible material will create airflow noise, however good the extractor is.
Can you have an extractor over a kitchen island?
Yes, using a ceiling extractor, suspended hood, downdraft system, or venting hob. The right choice depends on ceiling construction, duct route, island size, and the storage you can spare.
Plan Extraction Into Your Kitchen Design
Kitchen extraction works best when the appliance, the duct, and the cabinetry are designed as one. Left until the end, something always gives, and it is usually the duct diameter or a run of drawers.
Founded in 1983, Mayfair Kitchens has spent over 40 years designing kitchens for homes across Cheshire, Wirral, and the wider North West. If you are planning a kitchen renovation, settling these details early keeps a project moving cleanly from design through survey to installation.
Visit our Cheshire Oaks or Tarporley showroom, or contact our team to arrange a consultation. Let us help you create a kitchen that is truly built with you in mind.
0151 644 9100
0151 644 9100