How Much Sunlight Will My Window Get? A Room-by-Room Guide

The amount of natural light a room gets is one of those things people fall in love with on a viewing and then quietly regret six months later, once the season has turned. A living room that felt bright and airy in June can be gloomy by December, and a bedroom that seemed dim at the viewing might actually flood with morning light in summer. The good news is that sunlight is completely predictable. If you know which way a window faces and where you are on the planet, you can work out how much sun it will get on any day of the year, before you sign anything or move a single piece of furniture. This guide shows you how, and our sun position and shadow simulator does the arithmetic for you in 3D.

The two numbers that decide everything: elevation and azimuth

The sun's position in the sky at any moment is described by two angles. Elevation (or altitude) is how high the sun is above the horizon, from 0 degrees at the horizon to 90 degrees straight overhead. Azimuth is its compass bearing, measured clockwise from north: 90 degrees is due east, 180 degrees is due south, 270 degrees is due west. Together they tell you exactly where the sun is, and therefore whether it is shining through your window or hidden behind the wall.

A window only receives direct sun when the sun's azimuth falls within roughly 90 degrees either side of the direction the window faces, and the sun is above the horizon. A south-facing window (in the northern hemisphere) catches the sun whenever it is in the southern half of the sky, which is most of the daylight hours. A north-facing window barely sees direct sun at all in the northern hemisphere. East and west windows get sharp, low-angle light in the morning and evening respectively, but little at midday.

Why the season changes everything

The Earth's axis is tilted about 23.5 degrees, which is why the sun climbs much higher in summer than in winter. The effect is dramatic at mid-latitudes. Take London, at about 51.5 degrees north. Enter it into the simulator and check the midday sun on three dates:

• 21 June (summer solstice): the midday sun reaches about 62 degrees elevation, high and almost due south.
• 21 March (equinox): about 38 degrees — noticeably lower.
• 21 December (winter solstice): only about 15 degrees, skimming low across the southern sky.

That range, from 62 degrees down to 15 degrees, transforms a room. A high summer sun sits above the top of a south-facing window and pours light deep into the room but at a steep angle. The low winter sun, by contrast, streams almost horizontally through the same window, reaching much farther across the floor even though there is less of it and for fewer hours. This is exactly why a south-facing room can feel over-lit and hot in summer yet welcome every scrap of winter sun.

What each window orientation actually gets

Once you internalise elevation and azimuth, the orientations sort themselves out (descriptions are for the northern hemisphere; flip north and south below the equator):

• South-facing: the champion for daylight. Sun for most of the day year-round, highest and briefest in summer, low and long in winter. Best for living rooms and anywhere you want warmth and brightness.
• East-facing: direct morning sun as the sun rises in the east at low elevation, then shade from midday on. Lovely for bedrooms and kitchens where you want to wake with the light.
• West-facing: shaded mornings, then strong, warm, low-angle sun in the afternoon and evening. Can overheat on summer afternoons; great for a room you use after work.
• North-facing: almost no direct sun in the northern hemisphere, but soft, even, indirect light all day. Prized by artists and anyone who dislikes glare, but it needs help to feel warm.

A quick method to check any room

Here is a repeatable way to judge a room before you commit to it:

1. Find the window's facing direction. A phone compass held flat against the glass, pointing outward, gives you the azimuth the window faces.
2. Open the sun simulator and set your city (or latitude and longitude) and the date you care about most, often the darkest month, since that is the worst case.
3. Drag the time slider across the day and note the hours when the sun's azimuth is within about 90 degrees of your window's facing and its elevation is above zero. Those are your direct-sun hours.
4. Repeat for a summer date to see the seasonal range. If a room gets usable sun even in December, it will be bright all year.

Don't forget what's outside the window

The sun's geometry tells you when light could reach the window, but a neighbouring building, a wall, or a tall tree can block a low sun entirely. This is where thinking in shadows helps: an object of a given height casts a predictable shadow, and if your window sits inside that shadow, the geometry no longer matters. The same tool shows you shadow length and direction, and our companion guide on where shadows fall in a garden or yard walks through reading obstructions hour by hour. For a low winter sun at 15 degrees elevation, even a modest fence or hedge throws a shadow several times its own height, so a row of terraced houses opposite a south window can shade it for the whole winter.

Putting it to work

Whether you are choosing between two flats, deciding which room becomes the home office, or working out where to put a sun-loving houseplant, the process is the same: identify the window's direction, then let the sun's elevation and azimuth tell you the hours and seasons of direct light. Once you have the room mapped, you can plan the rest, from where the desk goes to how much paint you need if you redecorate, which our room paint and flooring calculator handles in the same 3D style. Light is free and predictable, so there is no reason to be surprised by it. Model it once, and you will never misjudge a room again.