How long is a building's shadow? A calculator and mid-winter table for Australian cities
How far a building's shadow reaches at 9am, noon and 3pm on 21 June in ten Australian cities, with a free calculator for any height, place and date.
A shadow diagram is drawn for a set day and set hours, in most of Australia 9am to 3pm on 21 June. Before anyone models a building, one question usually comes first: how far will its shadow reach? This page answers it for any height in any Australian city, with a calculator and a table worked out from the sun’s position on the day.
Key figures
- At noon on 21 June, a building’s shadow runs about 0.8 times its height in Darwin, 1.6 times in Sydney and 2.3 times in Hobart.
- By 9am that day it runs 5.5 times the height in Hobart and 2.2 times in Brisbane.
- A 9 m building in Sydney casts a shadow of about 26 m at 9am, 14 m at noon and 28 m at 3pm.
- The shortest shadow doesn’t fall at 12 o’clock: Sydney’s falls at about 11:57am, Perth’s at 12:18pm and Darwin’s at 12:48pm.
Shadow length calculator
Pick a city and a day, and enter the height. For each hour the planning rules usually test, you get the sun’s angle above the horizon, the length of the shadow on level ground and the direction it points.
On level ground, for a vertical edge of that height. Clock times are standard time, with no daylight saving.
Mid-winter shadows in ten Australian cities
Each figure is a multiplier: times it by the height of a wall or roof edge to get the length of its shadow on level ground.
| 9am | Noon | 3pm | Shortest of the day | |
|---|---|---|---|---|
| Sydney | 9am: 2.9× | Noon: 1.6× | 3pm: 3.1× | Shortest of the day: 1.6× at 11:57am |
| Melbourne | 9am: 4.5× | Noon: 1.8× | 3pm: 3.0× | Shortest of the day: 1.8× at 12:22pm |
| Brisbane | 9am: 2.2× | Noon: 1.2× | 3pm: 2.5× | Shortest of the day: 1.2× at 11:50am |
| Perth | 9am: 3.2× | Noon: 1.5× | 3pm: 2.4× | Shortest of the day: 1.4× at 12:18pm |
| Adelaide | 9am: 3.7× | Noon: 1.6× | 3pm: 2.7× | Shortest of the day: 1.6× at 12:17pm |
| Hobart | 9am: 5.5× | Noon: 2.3× | 3pm: 4.2× | Shortest of the day: 2.3× at 12:12pm |
| Darwin | 9am: 2.3× | Noon: 0.8× | 3pm: 1.1× | Shortest of the day: 0.7× at 12:48pm |
| Canberra | 9am: 3.3× | Noon: 1.6× | 3pm: 3.0× | Shortest of the day: 1.6× at 12:05pm |
| Gold Coast | 9am: 2.2× | Noon: 1.3× | 3pm: 2.6× | Shortest of the day: 1.3× at 11:48am |
| Newcastle | 9am: 2.8× | Noon: 1.5× | 3pm: 3.0× | Shortest of the day: 1.5× at 11:55am |
Download the data (CSV): every hour from 8am to 4pm on three days of the year, with the sun’s height and direction.
Hobart has the longest shadows because it sits furthest south, and Darwin the shortest because it sits closest to the equator. The gap between morning and afternoon comes from the clock. Eastern Standard Time is set by the sun at 150° east, close to Sydney, so Sydney’s 9am and 3pm shadows nearly match (2.9 and 3.1 times the height). Melbourne sits further west, its sun runs about 20 minutes behind the clock, and its 9am shadow (4.5 times) is much longer than its 3pm one (3.0 times).
How to work it out by hand
Shadow length is the height divided by the tangent of the sun’s angle above the horizon. At 9am on 21 June in Sydney the sun stands 19.0° up and tan(19.0°) is 0.344, so a 9 m wall casts a shadow of 9 ÷ 0.344, or about 26 m.
The shadow points directly away from the sun. The Australian winter sun stands in the north, so in Sydney a shadow swings from south-west at 9am, through south at noon, to south-east at 3pm.
How much the season changes it
Nothing moves the answer more than the date. At noon standard time in Sydney, a 9 m building’s shadow is about 14 m long on 21 June and under 2 m on 21 December, when the sun stands 79° up.
The test date matters for the same reason. Victoria’s Townhouse and Low-Rise Code tests 22 September rather than 21 June, and at 3pm in Melbourne the shadow then runs 1.4 times the height, against 3.0 times in mid-winter. Which day and hours apply where is set out in our state-by-state guide to shadow diagram rules.
Where this stops and a shadow diagram starts
The calculator gives you the length of one shadow on flat ground. It doesn’t know about a slope, which stretches a shadow downhill and shortens it uphill, or a neighbour’s wall or fence, which catches it. It doesn’t know the shape of your roof. And the planning tests measure more than length: usually how many hours of sun a window or a private open space keeps.
For those, the building has to be modelled on its site. The same model can then be rendered with the sun in its true position for that date and hour, so the picture and the diagram agree. Our guide to renders for planning submissions covers what assessors look for.
How we worked it out
The sun’s position comes from the equations behind NOAA’s Solar Calculator, which are based on Jean Meeus’s Astronomical Algorithms, with NOAA’s correction for atmospheric refraction. NOAA notes that it no longer maintains the calculator itself; the equations are unchanged. We checked our results against timeanddate.com’s solar noon figures for Sydney, Hobart and Darwin on 21 June 2026, and each matched to the tenth of a degree and within a minute.
Each city is taken at its centre, on its standard time, with the figures worked for 2026. They shift only slightly from year to year. A shadow’s far edge is soft, particularly with the sun low, so read a long shadow as an estimate. If you find an error, tell us and we will check it and correct the page.
More data and rule comparisons you can cite are on our research page. Have a project in mind? Send us the drawings and a line on what the renders are for. You’ll have a fixed price, a written scope and a delivery date within two business hours.