Drone 250g Weight Threshold in the UK

Why 250g Is the Key Dividing Line

The 250g threshold exists because of kinetic energy. A drone weighing under 250g, even in an uncontrolled descent, carries relatively low kinetic energy on impact. The risk of serious injury to a person struck by a sub-250g drone is significantly lower than for heavier aircraft. This risk-based reasoning underpins the entire UK Open Category framework, and 250g is where the CAA draws the first and most consequential line.

The threshold aligns with international practice. The European Union Aviation Safety Agency (EASA), the US Federal Aviation Administration (FAA), and aviation authorities in Australia, Canada, and New Zealand all use 250g as a regulatory boundary. The consistency reflects a broad consensus among aviation safety bodies about where meaningful risk begins.

For UK operators, the practical impact is immediate: a 249g drone and a 251g drone are subject to substantially different rules, even though the physical difference between them is negligible. The law draws a hard line, and operators need to know which side of it they fall on.

How the CAA Measures Drone Weight

The CAA uses Maximum Take-Off Mass, abbreviated MTOM. This is not the weight of the drone body alone. MTOM is the total mass of the aircraft as configured for flight, including:

• The airframe and all permanently attached components
• The battery (the heaviest battery the drone is designed to use)
• Propellers and propeller guards if fitted
• Any payload, including cameras, sensors, or delivery items
• Any accessories attached at the time of take-off

This definition matters because many popular drones sit very close to the 250g boundary. The DJI Mini series, for example, is marketed at 249g MTOM. Adding a third-party propeller guard, an aftermarket camera filter, or even a sticker wrap could push the aircraft above 250g, changing your regulatory category entirely.

If you are uncertain about your drone's MTOM, weigh it fully configured for flight on a calibrated scale. The specification sheet in the manufacturer's documentation lists the official MTOM, but your actual configuration may differ.

Below 250g: What You Can Do

Registration

If your sub-250g drone does not carry a camera, microphone, or any sensor capable of capturing personal data, and you fly it purely for recreation, you do not need to register with the CAA. No Operator ID is required. No Flyer ID is required.

However, the moment your sub-250g drone carries a camera or microphone, registration becomes mandatory. Since the overwhelming majority of consumer drones include an integrated camera, most sub-250g operators will still need to register. The registration process is completed online through the CAA website, and the Operator ID must be displayed on the drone.

Subcategory Access

Sub-250g drones, whether legacy or class-marked (C0/UK0), operate in the Open A1 subcategory. A1 is the least restrictive subcategory and permits flight in areas where uninvolved people are present. The key distinction between legacy and C0 class-marked drones at this weight is whether you can fly directly over uninvolved persons:

• C0/UK0 class-marked under 250g: Can fly over uninvolved people, provided the drone meets the 19-joule kinetic energy limit at terminal velocity.
• Legacy under 250g: Can fly near uninvolved people but must not intentionally fly directly over them.

Both can fly in residential and commercial areas. Both can fly in public spaces. The difference is the overflight restriction, which matters for operations such as event coverage, property surveys, or any flight path that would cross above pedestrians.

Where You Can Fly

Sub-250g operators in A1 can fly in towns, cities, parks, and near buildings. You must still observe the standard Open Category rules: maximum altitude of 120 metres above ground level, visual line of sight at all times, no flight in restricted airspace without CAA permission, and no flight within a Flight Restriction Zone around a protected aerodrome unless authorised.

Above 250g: What Changes

Mandatory Registration

Every drone operator with an aircraft weighing 250g or more must register with the CAA, regardless of whether the drone carries a camera. There are no exceptions for recreational use, toy drones, or first-time operators. Both an Operator ID and a Flyer ID are required. The Flyer ID is obtained by passing the CAA free online theory test, and both credentials must be renewed each year.

Subcategory Restrictions for Legacy Drones

Here is where the 250g threshold becomes most consequential for the majority of current operators. If your drone weighs more than 250g and has no class mark (legacy), you are restricted to the Open A3 subcategory. A3 requires maintaining a minimum horizontal distance of 150 metres from residential, commercial, industrial, and recreational areas.

This single restriction eliminates most urban and suburban flying locations. Parks, beaches, town centres, housing estates, industrial zones, and sports grounds are all off limits for legacy drones above 250g. You are effectively limited to open countryside, agricultural land, and remote coastal areas.

Class-Marked Drones Above 250g

Class-marked drones above 250g have access to less restrictive subcategories. A C1/UK1 drone (up to 900g, with kinetic energy below 80 joules) can operate in A1 near people. A C2/UK2 drone (up to 4kg) can operate in A2, flying within 30 metres of uninvolved people, or as close as 5 metres in low-speed mode (maximum 3 m/s). These expanded permissions are available only to class-marked aircraft flown by pilots holding the appropriate credentials.

The 250g Boundary and Insurance

There is no legal insurance requirement for recreational drone flights below or above 250g. However, commercial operators must hold appropriate third-party liability insurance regardless of drone weight. Many recreational operators choose to carry insurance voluntarily, particularly for drones above 250g where the potential for property damage or injury increases with mass.

The British Model Flying Association (BMFA) and other organisations offer membership packages that include third-party liability cover. Some home insurance policies may also cover drone use, though this varies significantly between providers and should be confirmed before relying on it.

Common Mistakes Around the 250g Threshold

• Assuming bare weight equals MTOM: A drone listed at 245g without its battery may exceed 250g once the battery is installed. Always check the MTOM with the heaviest battery option.
• Adding accessories without recalculating: Propeller guards, ND filters, GPS trackers, and payload attachments all add mass. If your drone sits at 249g MTOM, any addition may push it over.
• Confusing class mark benefits with legacy permissions: A 200g drone with no class mark has different permissions from a 200g C0 drone, specifically regarding overflight of uninvolved persons.
• Ignoring the camera registration trigger: Even below 250g, a camera-equipped drone requires Operator ID registration. The weight exemption from registration only applies to drones without cameras or microphones.

Summary

• Below 250g MTOM: Open A1 subcategory. Simplified registration (no camera = no registration needed). Can fly in populated areas. Legacy drones cannot overfly uninvolved people.
• 250g and above MTOM: Mandatory registration. Legacy drones restricted to Open A3 (150m from built-up areas). Class-marked drones access A1 or A2 depending on class.
• MTOM includes everything: Battery, accessories, payload. Weigh your drone as configured for flight.
• All standard Open Category rules still apply: 120m altitude ceiling, visual line of sight, restricted airspace rules, Flight Restriction Zones.