What extract rate does a UK kitchen cooker hood need?

Per Approved Document F Table 5.1b, a ducted cooker hood should extract 30 L/s (108 m³/h) minimum, though 60 L/s is recommended for effective capture. A recirculating hood should process 30 L/s. A general kitchen extract fan (not a hood) requires 13 L/s. Commercial kitchens typically need 120+ L/s depending on the cooking equipment.

Should I choose a ducted or recirculating cooker hood?

Ducted hoods are far more effective as they remove moisture, odours, and combustion gases (from gas hobs) directly to outside. Recirculating hoods only filter odour and grease — they cannot remove moisture or CO/CO2 from gas combustion. ADF guidance strongly favours ducted extraction, especially for gas cooking. Recirculating hoods may not satisfy Part F for gas hobs.

What size duct do I need for a cooker hood?

A minimum 150mm diameter rigid duct is recommended for domestic cooker hoods. For longer runs (over 5m) or multiple bends, 200mm diameter reduces pressure drop and noise. Never reduce below 100mm. Use rigid galvanised or plastic duct — avoid flexible duct for long runs as it has 3-5x higher friction loss.

Does a cooker hood need make-up air?

Yes, ducted cooker hoods extracting 60 L/s or more create significant negative pressure. Replacement (make-up) air must enter the kitchen through trickle vents, background ventilators, or a dedicated make-up air supply. Without adequate make-up air, the hood cannot achieve its rated flow rate, doors may slam, and back-draughting of flues can occur.

How wide should a cooker hood be?

The hood should be at least as wide as the cooker, ideally 50-100mm wider on each side for better capture. A 600mm cooker needs a 600-800mm hood. A 900mm range cooker needs a 900-1000mm hood. The bottom of the hood should be 650-750mm above the cooker surface for optimal capture without head clearance issues.

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Kitchen Cooker Hood Calculator — Extract Rate & Ductwork

Calculate cooker hood extract rates per Approved Document F, duct sizing to external discharge, and make-up air requirements for UK kitchens.

Hood Type

Ducted is strongly preferred per ADF

Cooker Type

Cooker Width

Hood Width

Should be >= cooker width

How We Calculate This

This calculator determines cooker hood extract rates per Approved Document F and sizes the ductwork to external discharge, including pressure drop estimation.

ADF extract rates

Ducted hood: 30-60 L/s (recommended 60 L/s)
Recirculating hood: 30 L/s
General extract (no hood): 13 L/s

Ductwork guidance

Duct must discharge to external air, not into a loft or cavity. Minimum 150mm diameter rigid duct. Each 90° bend adds equivalent of ~1m straight run. Total equivalent length should not exceed manufacturer's maximum for the hood model.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.