Direct answer: approximate measurements are enough for a first quote
For an initial quote, you do not need millimetre precision. Measure the visible opening, take clear photos and explain whether the job includes only the window, a shutter, a shutter box, mosquito screen or interior trims.
Final dimensions must always be checked by a professional before manufacturing or installation.
What to measure
Measure width and height in several points. Differences may reveal an uneven opening that needs careful finishing.
Also note opening type, shutter box, nearby radiators and any space limitations.
Useful photos
Send front photos, side details, the shutter box and the exterior when possible. These images help evaluate access, finishing and possible thermal bridges.
Items that change the price
Removal, shutter replacement, acoustic glass, security hardware, exterior access and masonry finishing can change the final cost significantly.
Common mistakes
Measuring only the glass.
Forgetting the shutter box.
Sending no side or exterior photos.
Confusing width and height.
Manufacturing without a final technical check.
Practical recommendation
Prepare a simple table with room, width, height, main problem and photos. This makes the quote more useful.