Which rooms get the sun depends on the way their windows face and on where you live. Choose your town, or type a latitude and longitude, and this tool works out, for walls facing each of the eight directions, the hours of direct sun on the 21st of every month this year, and for the month you pick, the times the sun is on each wall. It also gives sunrise, sunset, the height of the midday sun and the weeks, if any, when the midday sun passes to the north of overhead. The answer is astronomy, worked out for open ground. The classical texts read for this site give no rule for windows, so the result is practical, and it shows why popular Vastu asks for more windows to the north and east.
How it works
The sun’s position comes from the solar code of our Vedic site’s transit engine, the code that works out its sunrise and sunset, ported here unchanged. It uses the Meeus solar position, with sunrise and sunset taken when the upper edge of the sun meets the horizon under standard refraction. The tool turns the sun’s position into a height above the horizon and a compass bearing, minute by minute from sunrise to sunset.
A wall facing a direction has the sun in front of it while the sun is up and within 90 degrees of the way the wall faces. A wall facing east is one whose windows look east. The tool counts those minutes for each of the eight directions, on the 21st of each month, and joins them into the times shown.
We checked it against the Swiss Ephemeris for the eight places we test every tool with, from Gondia and Dhrangadhra to Lautoka in Fiji, London and New York, on the 21st of every month of 2026, and on dates in 1900 and 2074, at the equator and inside the Arctic Circle. The sun’s height agreed within 0.01 degrees and the minutes of sun on each wall within 2 minutes a day. Sunrise and sunset agreed within 8 seconds at those eight places on those days, and within 10 seconds on every day of 2026. Near the polar circles and beyond, the sun meets the horizon at a shallow angle, so the small difference in how the Swiss Ephemeris and the tool allow for the bending of light near the horizon matters more. On every day of 2026 at the places we tried, Reykjavik, Tromso, Murmansk, Longyearbyen and McMurdo in Antarctica, the tool’s sunrise and sunset were within 3 minutes of the Swiss Ephemeris, and within 25 seconds when the Swiss Ephemeris is given the tool’s own horizon line, the sun’s centre 0.833 degrees below the horizon. On the few days there when the sun only just dips below the horizon, or only just rises above it, the tool finds every time the sun’s centre crosses that line during the day. At 11 places from 60 to 78 degrees of latitude, on every day of 2026 and 2030, it found every one of those times that the Swiss Ephemeris gives for the tool’s own horizon line, within 38 seconds, and none that is not there; with the Swiss Ephemeris’s own allowance for the bending of light they were within 3 minutes.
The town list is the list of Indian towns our Vedic site uses for birthplaces, from GeoNames, shared under CC BY 4.0, and it is read from this site, so what you type in the town box is not sent to any map service. Once your email is confirmed, what you enter and the headline of the result are kept with your email, as the note under the form says, and you can delete them at any time. If you choose a town from the list, times are on India’s clock, UTC+5:30. For other places, type your clock’s standard difference from UTC, the one it keeps outside summer time, and add an hour to the summer months yourself where clocks go forward; without it the times are local sun time, in which the sun is highest close to noon.
Reading the result
The first line says where the midday sun stands on the 21st of your chosen month, how high it climbs, and which wall gets the longest sun. Below it, each wall has the times it is in sun that day, then a table gives the hours for every month.
For Mumbai on 21 June 2026 the sun rises at 6:02 am towards the east-north-east and sets at 7:19 pm towards the west-north-west, and at midday it stands 86 degrees up, a little to the north of overhead. A south-facing wall gets no direct sun that day, and a north-facing one has the sun in front of it from sunrise to sunset. Between the tropics this is normal for part of the year: in Mumbai the midday sun passes to the north of overhead from 16 May to 27 July 2026.
A high sun lights a wall at a slant and a short overhang shades it, so hours on a wall in summer count for less than the same hours in winter, when the sun is low. The afternoon sun on a west-facing wall is the one to shade in a hot climate.
Where traditions differ
Popular Vastu asks for more and larger windows on the north and east sides of a home, and fewer, smaller ones on the south and west. Our windows and ventilation guide records that the classical texts we read give no rule on window placement, and reads the modern rule as a matter of sun and heat: the north and east bring gentle light, the south and west bring heat.
South of the equator the sun is the other way round. The midday sun stands in the north for most or all of the year, so a north window there gets the strong sun. Vastu does not reverse its directions for the southern hemisphere, so our windows guide suggests following the sun there and treating the compass rule as a preference. The tool shows what the sun does at your place, whichever rule you follow.
What it does not do
It does not know what stands around your home. A neighbour’s building, a tree, a hill, a balcony above or a deep sunshade can keep the sun off a wall for much of the time shown, and cloud keeps it off on many days. It does not work out how hot a room gets or how much light comes in.
It scores nothing and predicts nothing, and it makes no claim about health or luck. To see which way your rooms face, use the phone compass, and to correct it for true north, the magnetic declination tool.
Frequently asked questions
↳ Which direction gets the morning sun?
In India walls facing north-east, east and south-east all have the sun from sunrise, all year. The east-facing wall keeps it until about midday. The north-east one keeps it longer in summer, and the south-east one longer in winter, when the sun stays in the south and goes on shining on it into the afternoon. Only in the far north of Ladakh, beyond about 35 degrees north, are the south-east wall's summer and winter hours about equal. The tool shows the exact times for your town.
↳ Why does my north-facing room get sun in summer?
In summer the sun rises north of east and sets north of west, so it shines on a north wall early and late in the day. Between the tropics it can also pass north of overhead at midday for some weeks: in Mumbai in 2026, from 16 May to 27 July.
↳ Is the sun the reason Vastu prefers windows to the north and east?
The classical texts we read give no window rule, so we cannot say what the reason was. Our windows guide reads the popular rule as a matter of sun and heat, and in most of India it suits the climate.
↳ Does it work for a place outside India?
Yes. Type the latitude and longitude and your clock's standard difference from UTC, the one it keeps outside summer time. Where clocks go forward in summer, add an hour to the times shown for the summer months. South of the equator the tool says so, because the midday sun stands in the north there.
↳ Why does the tool use the 21st of each month?
One fixed day a month gives a fair picture of the whole year and lets months be compared. The sun moves slowly, so a day or two either side changes the hours by only a little.
↳ Are the times exact?
For open ground, yes. At the eight places we test every tool with, sunrise and sunset were within 10 seconds of the Swiss Ephemeris on every day of 2026. Near the polar circles and beyond, where the sun meets the horizon at a shallow angle, they can be up to 3 minutes apart, including the few days when the sun only just dips below or rises above the horizon. On a real site, buildings and trees shade a wall for part of the time, so check the hours on the spot.