Cooker hood extraction rate calculator

When picking the right cooker hood for your kitchen you need to consider the power required to remove the volume of ‘used’ air created during your cooking.

This simple calculator works it out for you.  Remember, in larger open plan kitchens you should consider the total volume of the entire room including the dining area.
This works on the principle of changing the air 10 times per hour (you may need less if you are only doing light cooking).  You should start your extractor 10 minutes before and run it for 10 min after for best results.

If you are recirculating the exhaust from your hood (that’s when you can’t run ducting to an outside wall and you add a carbon filter to clean the air, but it stays within your kitchen), you will need a more powerful hood.  That’s because the filter adds an obstacle to the airflow and the the motors don’t run as efficiently. Ideally, you want a hood that achieves that level on at least the 2nd highest setting.  This means it wont be running at it’s loudest during normal operation and you have the option to turn it up again if you need a bit more extraction.

Another consideration is how the extraction rate has been reported in the product specs.  Some manufacturers report the m³/h according to EN 61591.  This is a great measurement as it give a real world rating at the end of 1.5m of ducting with a 90° bend. 

The other commonly used statistic is a often referred to as “unrestricted” which is the measurement directly off the hood.  This will obviously be higher rating than the EN 61591 and will make the hood performance seem much better than it is – somewhere in the region of 1/3rd.
Often manufacturers simply give the motor power, again this isn’t practical as a useable measurement as it doesn’t relate to any kind of real world usage.

You should endeavour to use 150mm ducting (or equivalent) wherever possible. The larger the ducting, the less air resistance is created. Rigid works significantly better than flexi as the ridges in bendy hoses significantly impact the smooth airflow.