Sun Altitude Calculator UK
Calculate real-time solar altitude, azimuth, solar noon, sunrise, sunset, and day length for any UK location.
Expert Guide: How to Use a Sun Altitude Calculator in the UK
A sun altitude calculator is one of the most practical tools you can use for solar design, architecture, photography, gardening, planning outdoor events, and even improving home energy performance. In the UK, where latitude spans roughly 50°N to 58°N for major population centres and extends farther north to around 60°N in island regions, solar angle changes are dramatic between seasons. That means a June midday sun can feel high, bright, and warm, while a December midday sun can remain very low above the horizon, producing long shadows and limited direct gain.
This page helps you calculate solar altitude for any UK location using date, time, latitude, longitude, and the right civil time setting (GMT or BST). You also get azimuth, solar noon, sunrise, sunset, and day length estimates, plus a chart of sun altitude through the day. If you are working on panels, shading, glazing, or garden layout, this gives you the practical geometry you need to make better decisions.
What is sun altitude?
Sun altitude is the angle of the sun above the horizon, measured in degrees. At sunrise and sunset, altitude is near 0°. If the sun is directly overhead, altitude is 90° (which never happens in the UK because of its latitude). At UK noon in summer, altitude can exceed 60° in southern areas, while in winter, midday values may be close to 10° in northern cities.
- 0° altitude: sun at horizon line.
- 10° to 20°: very low winter sun, long shadows.
- 40° to 65°: common UK summer midday range.
- Higher altitude: stronger shortwave radiation on horizontal surfaces and shorter shadows.
Why this matters in the UK specifically
Compared with lower-latitude countries, the UK experiences large seasonal variation in both sun altitude and day length. This has direct implications:
- Solar PV yield: panel tilt and orientation strategy changes with latitude and intended seasonal output profile.
- Building design: south-facing glazing can benefit from winter sun but needs summer overheating control.
- Urban planning: low winter sun causes long shadow footprints from buildings and trees.
- Photography and film: golden hour duration and sun path direction vary strongly by season and region.
- Agriculture and gardening: crop and greenhouse placement depends on winter shading risk and summer exposure.
The core astronomy behind the calculator
The calculator uses standard solar geometry approximations that are widely used in engineering tools. It computes the solar declination for the day of year, equation of time correction, and hour angle from local civil time plus longitude correction. From there, it solves the solar zenith angle and converts that to altitude using:
Altitude = 90° – Zenith
You also get solar azimuth (direction of the sun), and estimated sunrise and sunset using the common apparent horizon correction (about 90.833° zenith to include refraction and solar disc effects). This is suitable for practical planning and educational use.
UK city comparison: solar noon altitude statistics
The table below shows representative noon sun altitude values for selected UK cities on key annual dates. These values are based on latitude geometry and rounded to two decimal places.
| City | Latitude (°N) | Noon Altitude (June Solstice) | Noon Altitude (Equinox) | Noon Altitude (December Solstice) |
|---|---|---|---|---|
| London | 51.51 | 61.93° | 38.49° | 15.05° |
| Birmingham | 52.49 | 60.95° | 37.51° | 14.07° |
| Manchester | 53.48 | 59.96° | 36.52° | 13.08° |
| Cardiff | 51.48 | 61.96° | 38.52° | 15.08° |
| Belfast | 54.60 | 58.84° | 35.40° | 11.96° |
| Edinburgh | 55.95 | 57.49° | 34.05° | 10.61° |
| Inverness | 57.48 | 55.96° | 32.52° | 9.08° |
| Plymouth | 50.38 | 63.06° | 39.62° | 16.18° |
Interpretation: the same winter date can produce a noon altitude difference of roughly 7° between parts of southern and northern UK, which is significant for shading and solar gain.
UK day length comparison statistics
Day length changes strongly with latitude. Approximate daylight durations for key cities are shown below. Exact values vary slightly year to year due to orbital factors and local horizon effects.
| City | Approx Day Length (June Solstice) | Approx Day Length (December Solstice) | Seasonal Difference |
|---|---|---|---|
| London | 16h 38m | 7h 50m | 8h 48m |
| Cardiff | 16h 33m | 7h 55m | 8h 38m |
| Birmingham | 16h 27m | 7h 58m | 8h 29m |
| Manchester | 16h 42m | 7h 42m | 9h 00m |
| Belfast | 17h 07m | 7h 20m | 9h 47m |
| Edinburgh | 17h 37m | 6h 57m | 10h 40m |
| Inverness | 17h 50m | 6h 45m | 11h 05m |
How to use this calculator accurately
- Use a reliable coordinate pair for your exact site, not just city centre values.
- Choose UK auto time mode unless you intentionally want fixed GMT or fixed BST.
- Check multiple dates (solstices, equinoxes, and project-critical months).
- For shading studies, run several times per day, not only noon.
- For PV and thermal work, combine altitude with azimuth and local obstruction data.
Common practical use cases
1) Solar panel planning: If your roof has partial obstructions from chimneys, dormers, or nearby trees, the winter low-altitude sun can create disproportionately large losses in morning and afternoon periods. A daily altitude curve helps identify when the sun clears obstructions.
2) Passive solar design: South-facing windows can contribute useful winter heat at low sun angles but may cause overheating in late spring and summer. By comparing noon altitude and high-summer shoulder hours, you can size overhangs more effectively.
3) Garden and landscape design: Raised beds, hedges, and pergolas can be arranged based on seasonal altitude so that key planting areas keep winter access to low-angle sun while receiving manageable summer shade.
4) Real estate and development: Overshadowing risk in UK planning contexts often depends on low solar altitudes in colder months. Early-stage envelope studies benefit from fast altitude checks at specific local times.
5) Creative work: Photographers can use altitude and azimuth to plan side lighting, front lighting, and silhouette timing. In the UK, the same clock time can have very different sun positions across seasons.
Interpreting azimuth with altitude
Altitude alone tells you how high the sun is, but not where it is horizontally. Azimuth fills that gap. In practical terms:
- Morning sun appears in eastern azimuth sectors.
- Solar noon is generally toward the south in the UK.
- Evening sun shifts to western azimuth sectors.
- At high summer latitudes in the UK, sunrise and sunset azimuth spread is wider than in winter.
Data quality and limitations
This calculator provides robust engineering-level approximations for everyday planning. However, real-world outcomes also depend on terrain, skyline obstructions, atmospheric conditions, and exact timestamp handling near daylight saving transitions. For legal, survey-grade, or bankability-grade analysis, combine this with specialist solar simulation software and verified geospatial datasets.
Authoritative references
For deeper methodology and official weather context, consult these sources:
Final takeaway
A UK sun altitude calculator is not just a technical curiosity. It is a decision tool. Whether you are optimizing a roof array in Bristol, checking winter light in Edinburgh, or planning summer shading in London, understanding altitude and daily solar path can materially improve outcomes. Use this calculator as a fast first-pass analysis, then layer in site-specific details for best results.