How powerful does a cooker hood actually need to be? Extraction figures can range from a few hundred cubic metres per hour to 900m³/h or more, but the biggest number is not automatically the right answer. The useful figure is the airflow your kitchen needs, based on the volume of the room and whether the hood is ducted outside or recirculating.
The quick answer
- Measure the length × width × height of the kitchen in metres.
- Multiply the room volume by 12 air changes per hour.
- For recirculation, allow for around a one-third reduction in effective airflow.
- That means a recirculating hood needs a rated airflow around 50% higher than the ducted target.
- In an open-plan kitchen, calculate the volume of the whole connected space, not just the area around the hob.
- When comparing hoods, look for airflow measured to BS EN IEC 61591 / EN IEC 61591.
Cooker Hood Extraction Rate Calculator
Enter your room dimensions and installation type. We use 12 air changes per hour and apply a 33% airflow allowance when recirculating.
Find a ViandPro hood that meets your result
We’ll show in-stock models at or above your required extraction rate, then you can filter by hood type and width.
Compatible cooker hoods
These in-stock models meet or exceed your calculated extraction requirement. Refine the results by installation type and width.
How the calculation works
A cooker hood is trying to capture and remove contaminated cooking air faster than it can spread through the room. A simple way to size the fan is to use air changes per hour, usually shortened to ACH.
For this calculator we use 12 air changes per hour. That gives more extraction reserve than the traditional 10 ACH rule and suits the way modern kitchens are often used, particularly larger open-plan spaces and higher-output cooking.
For example, a kitchen measuring 4m × 4m with a 2.4m ceiling has a volume of 38.4m³.
38.4 × 12 = 460.8m³/h, so we would treat approximately 461m³/h as the basic ducted extraction target.
Why recirculation needs more power
A ducted cooker hood sends the extracted air outside. A recirculating hood has to push the air through additional filtration before returning it to the room. That extra resistance reduces the effective airflow available at the hood.
For planning purposes, our calculator assumes a recirculating installation loses around one third of the hood’s effective extraction performance.
If only two thirds of the rated airflow remains effective, you cannot simply add 33% to the required number. To end up with the same effective airflow, the hood rating needs to be multiplied by 1.5.
So the 461m³/h kitchen example above would need a recirculating hood rated at approximately 691m³/h.
Typical kitchen examples
| Room size | Volume | Ducted target at 12 ACH | Recirculating rated target |
|---|---|---|---|
| 3 × 3 × 2.4m | 21.6m³ | 259m³/h | 389m³/h |
| 4 × 4 × 2.4m | 38.4m³ | 461m³/h | 691m³/h |
| 5 × 4 × 2.4m | 48m³ | 576m³/h | 864m³/h |
| 6 × 4 × 2.4m open-plan space | 57.6m³ | 691m³/h | 1,037m³/h |
These numbers also show why high extraction figures can be genuinely useful rather than just marketing. In a larger kitchen, or when using recirculation, a 700-900m³/h hood can provide useful working headroom instead of forcing the fan to run at maximum every time you cook.
Do not size a hood to run flat-out all the time
The calculated number is a useful minimum planning target, not the point at which you should stop comparing products. Ideally, normal cooking should be handled below the hood’s maximum speed.
That gives you three advantages: lower day-to-day noise, reserve power for frying or searing, and less need to run the motor at full output for long periods.
This is one reason ViandPro focuses strongly on extraction performance. Extra airflow capacity is useful when it gives you the option to achieve the airflow your kitchen needs without living on the loudest setting.
Look for EN 61591 tested airflow figures
A headline airflow figure is only useful if you know how it was measured. In the UK, BS EN IEC 61591:2023 is the current standard covering methods for measuring the performance of household cooking fume extractors. The European and international versions are EN IEC 61591 and IEC 61591.
The standard includes a defined method for measuring volumetric airflow. That matters because it creates a common test method, making figures from different products much more meaningful to compare.
When shopping, look for wording such as “airflow measured to EN 61591” or a clear reference to BS EN IEC 61591 / EN IEC 61591 in the specification or technical documentation.
If a manufacturer quotes an unusually high extraction figure without stating the measurement method, be careful about comparing it directly with a figure measured to EN 61591. A motor’s theoretical or unrestricted airflow is not necessarily the same thing as a cooker hood’s performance under a standardised test.
What else reduces real-world extraction?
The calculator sizes the hood from room volume. The installation can still have a major effect on what you actually get in the kitchen.
- Undersized ducting: reducing a 150mm outlet into a much smaller duct increases resistance.
- Too many bends: every tight bend makes the fan work harder.
- Long duct runs: the further air has to travel, the more pressure is lost.
- Restrictive grilles and vents: poor external terminals can choke airflow.
- Dirty grease filters: blocked filters reduce the amount of air that can pass through the hood.
- Saturated carbon filters: recirculating hoods need their filters maintained or replaced as specified.
If your calculated requirement is close to the maximum rating of the hood, choosing the more powerful model usually gives a better margin for these real-world losses.
For more on installation, see our guide to ducted vs recirculating cooker hoods and our guide to reducing cooker hood noise.
What about open-plan kitchens?
This is where people most often underestimate the required airflow. If your kitchen opens directly into a dining or living area with no door separating the spaces, use the dimensions of the whole connected room.
A 3m × 4m kitchen area may look small on a plan, but if it forms part of a 7m × 5m kitchen-diner, the extractor is working within that much larger air volume.
Should the hood be wider than the hob?
Extraction rate and capture area are different things. A powerful motor cannot fully compensate for a hood that is badly positioned or too narrow to capture the rising cooking plume.
As a general rule, choose a hood at least as wide as the hob. Where the installation allows it, a slightly wider hood can improve capture, particularly for ceiling and island extraction where the hood sits further away from the cooking surface.
How long should you run the cooker hood?
Switching the hood on before cooking helps establish airflow before steam, grease and odours build up. It is also worth leaving the hood running for a short period after cooking has finished.
For everyday use, around 5-10 minutes beforehand and 10-15 minutes afterwards is a useful starting point, although heavy frying or strong cooking odours may justify longer.
Frequently asked questions
How many air changes per hour should a cooker hood provide?
For this ViandPro sizing guide we use 12 air changes per hour. Multiply the room volume in cubic metres by 12 to calculate the ducted airflow target.
How much extraction do I lose when recirculating?
For planning purposes, we allow for around a one-third reduction in effective airflow. To compensate, multiply the ducted airflow requirement by approximately 1.5 when selecting the hood’s rated extraction.
Is 600m³/h a powerful cooker hood?
It can be very suitable for a typical kitchen, but room size matters. A 600m³/h hood gives much more headroom in a 30m³ kitchen than it does in a large open-plan room.
What does EN 61591 mean on a cooker hood?
EN IEC 61591 is the European standard that specifies methods for measuring cooker hood performance, including volumetric airflow. A declared EN 61591 airflow figure gives you a much better basis for comparing products tested using the same method.
Do bends in cooker hood ducting reduce extraction?
Yes. Long runs, narrow ducting and tight bends increase resistance and can reduce the airflow delivered by the installed hood. Keep ducting as short, smooth and correctly sized as practical.
Do I include the dining area in an open-plan kitchen calculation?
Yes. If the spaces are directly connected, use the volume of the whole room rather than just the kitchen cabinet area.
Need more extraction headroom?
Explore ViandPro wall, ceiling, island and downdraft cooker hoods, including high-airflow models designed for demanding kitchens and recirculating installations.
Calculator note: this is a practical sizing guide rather than a building-services calculation. Actual installed airflow depends on the hood, filters, duct diameter, duct length, bends, terminals and installation conditions.