Getting accurate window measurements is the single most important step when ordering plantation shutters. Even the highest-quality shutters will look wrong if they don't fit properly, and mistakes can be costly—most custom shutters cannot be returned. This guide walks you through the measuring process step by step, whether you're planning an inside mount or outside mount installation.
Key Takeaway
Always measure each window individually, even if they appear identical. Australian homes, especially older properties, often have slight variations between windows that look the same. Record measurements in millimetres for maximum accuracy.
Tools You'll Need
Before you start measuring, gather these essential tools:
- Steel tape measure: At least 3 metres long. Avoid fabric tape measures as they can stretch and give inaccurate readings.
- Step ladder: For safely reaching the top of tall windows.
- Notepad and pen: To record measurements immediately. Don't rely on memory.
- Spirit level: To check if your window frames are square.
- Pencil: For marking measurement points on the frame.
Understanding Inside vs Outside Mount
Before measuring, you need to decide which mounting style suits your windows. This choice affects how you measure and the final appearance of your shutters.
Inside Mount (Reveal Fit)
Inside mount shutters fit within the window reveal—the recessed area of your window frame. This is the most popular choice in Australia because it creates a clean, built-in look that showcases architectural details. Inside mounting works best when your window reveal is at least 60mm deep (75mm is ideal) and the frame is relatively square.
Outside Mount (Face Fix)
Outside mount shutters attach to the wall or face of the window frame, covering the entire window opening. This option works well for shallow reveals, windows that aren't perfectly square, or when you want to make windows appear larger. Outside mounting requires a flat, stable surface for attachment.
Pro Tip
If your window reveal depth varies significantly (more than 5mm difference across the opening), consider outside mounting instead. Trying to force an inside mount on an uneven reveal often results in visible gaps.
Measuring for Inside Mount
Inside mount measurements require precision because the shutters need to fit within the opening with minimal gaps. Follow these steps carefully:
Step 1: Check the Reveal Depth
Measure from the front edge of your window reveal (where the shutter will sit) to the glass or window sash. You need at least 60mm depth for most plantation shutters. If your reveal is shallower, you'll need to consider outside mounting or specialised shallow-reveal shutters.
Step 2: Measure the Width
This is where most mistakes happen. You need to measure the width at three points:
- At the top of the opening
- At the middle of the opening
- At the bottom of the opening
Record all three measurements. The narrowest measurement is typically the one you'll use, but check your shutter supplier's specific requirements—some prefer the average or have their own deduction calculations.
Step 3: Measure the Height
Similarly, measure the height at three points:
- On the left side of the opening
- In the centre of the opening
- On the right side of the opening
Again, record all measurements. Height variations are common in older Australian homes where settling has occurred over decades.
Step 4: Check for Square
Use your spirit level to check if the reveal is plumb (vertical) and level (horizontal). Measure the diagonals of the opening—if they're within 3mm of each other, your window is reasonably square. Larger differences may require outside mounting or custom adjustments.
Measurement Checklist for Inside Mount
- Reveal depth: minimum 60mm required
- Width: measured at top, middle, and bottom
- Height: measured at left, centre, and right
- Diagonals: within 3mm for square fit
- Note any obstructions (handles, locks, tiles)
Measuring for Outside Mount
Outside mounting is more forgiving but still requires careful measurement to ensure proper coverage and a balanced appearance.
Step 1: Determine Coverage
Decide how much overlap you want around the window opening. A standard recommendation is 50-75mm on each side to ensure good light blockage and a balanced look. Consider any obstructions like power points, light switches, or adjacent walls.
Step 2: Calculate Width
Measure the width of your window opening, then add your desired overlap on each side. For example, if your opening is 900mm wide and you want 60mm overlap each side, your total shutter width would be 1020mm.
Step 3: Calculate Height
Measure from where you want the top of the shutters to where you want the bottom. Consider whether you want them to sit on the window sill or extend past it. If extending past the sill, account for adequate clearance from the floor if applicable.
Step 4: Check the Mounting Surface
Ensure the wall or frame where you'll attach the shutters is flat and capable of holding screws securely. Brick, timber, and plaster walls are generally fine. For cement render or other surfaces, you may need specific fixings.
Common Measuring Mistakes to Avoid
After years of helping Australians with their shutter projects, these are the most frequent errors we see:
- Rounding measurements: Never round to the nearest centimetre. Shutters are made to millimetre precision.
- Measuring once: Always measure twice, ideally at different times of day when lighting varies.
- Ignoring obstructions: Window handles, security sensors, and decorative mouldings can all interfere with shutter operation.
- Forgetting tile thickness: In bathrooms and kitchens, measure from the tile surface if tiles extend into the reveal.
- Assuming symmetry: Even in new homes, windows may not be perfectly identical.
Special Window Types
Some windows require additional considerations:
Bay Windows
Measure each section of a bay window separately. Pay special attention to the angles where panels meet—accurate angle measurements are critical for a seamless fit.
Arched Windows
For arched windows, you'll need the width, the straight height (from sill to where the arch begins), and the total height to the top of the arch. Many suppliers also need the radius of the arch.
French Doors
When fitting shutters to French doors, consider clearance for door handles and ensure the shutters won't interfere with door operation. You'll also need to account for the doors swinging open.
When to Get Professional Measurement
If you have multiple windows, unusual shapes, or aren't confident in your measuring skills, consider paying for professional measurement. Many shutter companies offer this service, and the cost is often offset against your order. Professional measurers also take responsibility for any errors.
Recording Your Measurements
Create a simple diagram for each window showing:
- Room location (e.g., "Master Bedroom - North Wall")
- All width measurements
- All height measurements
- Reveal depth
- Mounting style (inside or outside)
- Any obstructions or special notes
Take photos of each window from both inside and outside. These references are invaluable when ordering and can help resolve any questions with your supplier.
Next Steps
Once you have accurate measurements, you're ready to start shopping for shutters. Consider our guides on choosing the right louvre size and selecting materials for Australian conditions to make informed decisions about your purchase.