How to Measure for a Window, Door or Patio Awning

Key takeaways

• Always measure the opening (door, window or patio doors) first, then add the extra width you want for coverage and visual balance on each side.
• Mounting height, projection and slope all work together: too low or too flat and you risk banging your head or collecting rainwater; too high and you lose effective shade.
• Note down any obstructions such as gutters, soil pipes, vents and lights before you commit to a size; a compact front door canopy such as the VOUNOT 120 x 80 cm awning can be easier to position neatly above a busy doorway.
• For patio awnings, think about how the sun moves across your garden and choose a width and projection that will actually shade your seating area at the times you use it most.
• Measure at least twice, write everything down and cross-check the manufacturer’s technical diagram before ordering.

Why measuring for an awning matters

An awning is a semi-permanent feature fixed to your home, so getting the size and position right first time is important. Unlike a freestanding parasol or pop-up canopy, a wall-mounted awning is designed around your doors, windows and outdoor space. If it is too small, it will not provide enough shelter where you actually need it; if it is too big or badly positioned, it can look out of scale or even obstruct doors, windows and paths.

Accurate measuring also affects how well the awning performs. For example, the projection (how far it comes out from the wall) and the angle of slope will determine how well rain runs off and how much shade you get throughout the day. The mounting height has to give you enough headroom under the lowest edge, while still leaving space above the door or window for the brackets and casing.

Good measuring reduces the risk of expensive returns or modification work. Many fixed door canopies, such as compact polycarbonate models, have set widths and projections, so you choose the closest fit. Larger retractable patio awnings often come in standard width increments, and you may need to consider whether there is solid masonry in exactly the right place for the brackets. Spending a little extra time with a tape measure, spirit level and notepad can save you a lot of hassle later.

The three core measurements: width, projection and height

Almost every awning, from a small front door canopy to a wide patio awning, is described using three core measurements:

• Width – how wide the awning or canopy is along the wall.
• Projection – how far it extends out from the wall.
• Mounting height – the height at which you fix the brackets or back rail.

It helps to imagine a sideways ‘L’ shape when viewed from the side: the upright of the ‘L’ is your wall and mounting height, the horizontal part is the projection, and the length along the wall is the width. Throughout this guide, you will use this simple mental picture to keep measurements clear in your mind.

Tools and preparation

Before you start measuring, gather a few basic tools:

• Sturdy tape measure (5 m or longer is useful for patios)
• Spirit level or a long, straight edge
• Notepad or measuring worksheet and a pencil
• Step ladder, used safely with help if needed
• Masking tape or chalk to mark key points on the wall

It is a good idea to sketch a simple front view and side view of the wall or opening and write measurements directly on these sketches. This makes it easier to compare with the manufacturer’s diagram later.

Tip: When you measure, note whether each dimension is the size of the opening (door or window) or the size of the awning you are considering. Mixing the two on your notes is a common source of mistakes.

How to measure for a door awning or front door canopy

Door awnings and canopies are usually smaller, fixed units designed mainly for rain protection and a bit of shade. They are common above front doors, back doors and French doors.

Step 1: Measure the door width and frame

Measure the total width of your door and surrounding frame, from the outside edge of the frame on one side to the outside edge on the other. If you have sidelights (fixed glass panels either side of the door), decide whether you want the canopy to cover just the door or the entire entrance.

Add at least 5–10 cm on each side of the door frame to get a practical minimum canopy width. For example, if your door and frame are 90 cm wide, aim for an awning width of at least 100–110 cm. This gives a little overhang and looks more proportionate.

Step 2: Decide the projection you need

For a simple rain canopy over a door, a projection of around 70–90 cm usually works well. This is enough to keep the area in front of the threshold dry while you unlock the door, without sticking out so far that it dominates a small façade.

Compact models such as a rigid polycarbonate door canopy with around 75 cm projection are typical. Check that the projection does not create a head height issue over steps or a narrow path; you want to be able to walk under it comfortably.

Step 3: Check mounting height and door clearance

Measure from the ground (or top of any step) up to the top of the door frame. For many homes this is roughly 2.0–2.2 m. You will usually want at least a few centimetres of wall above the frame to mount brackets or a canopy rail.

Allow for how the door opens. For outward-opening doors, you must ensure that the door can swing fully without hitting the underside of the canopy. Measure the height of the door leaf and how much space you need above the top of the frame for it to clear any awning supports.

Step 4: Look for obstacles around the doorway

Stand back and look at the wall around your door. Make a note of anything that might interfere with a canopy, for example:

• Gutters and downpipes
• Alarm boxes or cameras
• External lights
• Extractor fan vents

You may be able to choose a slightly narrower canopy to fit between a pipe and a light, or pick a model that can be joined or extended later. Some modular canopies can be installed side by side if you need extra width across a longer wall.

Worked example: measuring for a simple front door canopy

Imagine your front door and frame measure 92 cm wide, and the distance from the top of the frame to the underside of the gutter is 35 cm. You have an external light 25 cm to the right of the frame.

• You add 9 cm each side for overhang, giving a target canopy width of around 110 cm.
• You check product options and find a 120 cm wide canopy, which will extend slightly past the light. You decide that is acceptable, or you plan to move the light.
• You measure from the ground to the top of the frame and get 205 cm. With 35 cm of wall above, your mounting height will be around 215–220 cm, leaving room under the gutter.

This combination would allow a prefabricated unit such as a VOUNOT 120 x 80 cm door awning, provided you are happy with the slight overlap near the light or adjust its position.

How to measure for a window awning

Window awnings are mainly about shade and glare control, particularly for south- and west-facing rooms. They may be fixed or retractable, but the measuring principles are similar.

Step 1: Measure the window opening and surrounds

Measure the full width of the window including its frame. Decide how much wider you want the awning to be on each side. A common rule of thumb is to extend at least 10–20 cm beyond the frame on each side to block low-angle sun and reduce light leakage.

If the window is part of a group (for example a wide bay or several units close together), consider whether you want a single wide awning or separate units. For one large awning, measure from the outermost edge on the left to the outermost edge on the right, then add some overhang.

Step 2: Choose a projection for sun control

The projection you need depends on the height of the window, how far above the ground it sits, and how much sun you want to block. For upper-storey windows, even a modest projection can make a big difference to glare and indoor temperatures.

As a rough guide, for typical UK sun angles, a projection of about half the window height will significantly cut high summer sun while still letting in lower winter light. For example, if your window is 120 cm tall, a projection around 60–80 cm may be effective. You can fine-tune this based on which hours of day you most want shade.

Step 3: Check mounting height, especially on upper floors

Measure from the bottom of the window to the ground, then from the top of the window to any eaves, guttering or overhang. This tells you how much vertical space you have to fix brackets or cassettes. You should try to mount window awnings high enough that the bottom edge does not sit awkwardly across the view, unless it is a drop-arm or vertical screen designed for privacy.

On upper floors, you will usually be fixing into solid masonry below the roofline. Note the wall material (brick, block or render) so you can choose the right fixings and confirm that the area is strong enough for the wind load of the awning.

How to measure for a patio awning

Patio awnings (often retractable) cover larger areas and involve more decisions. They are popular over outdoor dining areas, seating zones and bifold or French doors.

Step 1: Measure wall space and door or window width

First, measure the total width of the doors or windows the awning will cover. For French doors or standard patio doors, many people prefer the awning to extend at least 20–30 cm beyond the frame on each side to create a balanced look and better shade.

Next, measure the available wall space where the brackets could sit. Check for obstructions such as downpipes, soil pipes, vents, satellite dishes or light fittings. Your chosen awning width must fit comfortably between these, leaving at least a few centimetres clearance to avoid clashing.

Step 2: Decide how far the awning should extend

Awnings for patios and seating areas can have projections from around 2 m for compact models up to 3.5 m or more for larger terraces. To work out what you need, measure from the wall out to where you usually place your table, chairs or loungers.

As a simple written ‘diagram’, imagine a line on the ground from the wall to your seating:

• Wall to edge of dining table: for example, 2.2 m
• Allow room for chairs when pulled back: add 0.6 m
• Comfortable shaded zone beyond chairs: add 0.3–0.5 m

In this example, you might look for an awning with a projection of around 3.0–3.5 m. This should give shade over both the table and people sitting around it, even as the sun moves during the day.

Step 3: Mounting height and comfortable headroom

Patio awnings are usually fixed to the wall above doors, often just below the gutter. Measure from the ground to the underside of the gutter or soffit to see how much room you have. Most people find a clear head height of around 2.0–2.2 m under the lowest front edge of the awning comfortable.

Remember that retractable awnings need to be installed with a slope so rainwater runs off. This means the mounting height at the wall will be higher than the front edge. For example, if the front bar is at 2.1 m and you use a drop of about 15 cm per metre of projection on a 3 m awning, the wall mounting height might be around 2.55 m.

Step 4: Think about UK sun angles and orientation

In the UK, the sun is never straight overhead, and its path varies with the seasons. South-facing patios get the most direct sun, while east- and west-facing areas get stronger sun in the morning or late afternoon. To choose an effective size:

• For south-facing patios, a larger projection will help block midday sun from high angles.
• For west-facing seating areas, width and side overhang can matter as much as projection to deal with low evening sun.
• If you mostly sit close to the house wall, you may not need an extra-deep projection, but you will still want good overhang beyond the door width.

Try standing where you normally sit and look back at the wall, imagining the awning width and depth in place. This mental test often reveals whether the size you had in mind actually covers the area you use.

Tip: If possible, visit your patio at the time of day you most want shade and note where the sun falls. This can help you decide whether to prioritise extra width or extra projection.

Allowing for doors, windows and obstacles

Any opening element under your awning must be able to move freely. This includes:

• Outward-opening doors
• Tilt-and-turn windows
• Bifold and sliding doors

Measure the swing or movement of the door or window and check it against the manufacturer’s side profile or section drawing. Ensure that when fully open, the panel does not hit the arms, fabric, or underside of a fixed canopy.

Also consider wall-mounted items that might need future maintenance or access, such as boiler flues or vents. Try to avoid placing an awning in a position that makes safe access to these features impossible without removing it.

Checking wall construction and fixing positions

Before committing to an awning size, check that the area of wall you plan to use is structurally suitable:

• Brick or solid block is usually ideal for fixing brackets.
• Rendered walls may need special fixings to go through to solid material behind.
• Cavity walls and lightweight cladding need careful consideration and possibly professional advice.

Measure where the brackets will sit, not just the overall width. For larger patio awnings, the mounting brackets often sit a set distance in from each end, so you should check for any obstruction exactly where those brackets will land. Manufacturer diagrams usually give these measurements; compare them with your sketch of pipes, lights and other features.

Worked sizing examples

Example 1: Awning for French doors

You have French doors 150 cm wide leading onto a small patio, and you want a retractable awning mainly for shade.

• Door width: 150 cm.
• You add 25 cm each side, giving a target awning width of 200 cm.
• Your seating area begins about 1.5 m from the wall; you choose a 2.5 m projection so that the table and chairs are under shade.
• Mounting height below the gutter is 2.5 m, and you plan for the front edge to be around 2.1 m high, giving comfortable headroom.

Example 2: Awning for bifold doors

You have 4-panel bifold doors 3.0 m wide opening onto a deck. You want to shade the deck area used for dining.

• Door width: 300 cm.
• You add 30 cm each side, aiming for an awning width of 360 cm if space allows.
• The deck extends 3.5 m from the wall; you choose a 3.0–3.5 m projection, depending on available models.
• You confirm that the bifold panels stack inside, so they will not clash with the arms or front bar when the doors are open.

Common measuring mistakes to avoid

Many awning problems trace back to a handful of simple measuring mistakes:

• Measuring the wrong item – confusing the size of the opening with the overall awning size, then ordering something too small.
• Ignoring gutters and pipes – discovering too late that a downpipe sits exactly where a bracket needs to go.
• Forgetting headroom – choosing a projection and slope that bring the front edge too low over steps or paths.
• Underestimating sun angles – picking a shallow projection that looks good on paper but does not actually shade the table or doors when the sun is at its strongest.
• Not checking door and window movement – especially with outward-opening or tilt-and-turn designs.

Warning: Never rely solely on approximate product descriptions. Always compare your measurements with the detailed technical drawing or specification sheet before ordering.

Helpful ready-made sizes and examples

Many small door canopies and basic awnings come in standard sizes that suit typical UK door and window widths. If your measurements are close to these sizes, a ready-made model can be a practical solution.

Compact front door canopies around 100–120 cm wide and 70–80 cm projection work well for single doors. For instance, a VOUNOT 120 x 80 cm canopy or a 100 x 75 cm rigid polycarbonate canopy can cover most standard front or back doors when installed at a suitable height.

For wider doors or small patios, you may find that two identical canopies can be installed side by side to create a longer run; just be careful to measure so that joints sit neatly between door and window frames. If your space or needs are less typical, a retractable awning with a broader range of width and projection options may be worth exploring, alongside guidance such as our fixed vs retractable awnings comparison.

Conclusion

Measuring for a window, door or patio awning is mostly about slowing down and working methodically. Start with the width of the opening you want to protect, then think through the projection, mounting height and any obstacles that might affect where brackets and casings can sit. By sketching your wall, double-checking each dimension and comparing your notes with the manufacturer’s diagrams, you can choose an awning that looks right and performs as intended.

Once you have reliable measurements, you can confidently compare different awning types and materials, from simple fixed door canopies to more substantial retractable patio models. Smaller ready-made canopies, such as compact polycarbonate units for front and back doors, can fit neatly into the measurements you have taken, while larger awnings benefit even more from precise planning.

With your measurements in hand and an understanding of how width, projection and mounting height work together, you are well placed to choose an awning that adds both comfort and curb appeal to your home for the long term.