Solar Panel Tilt Angle Calculator

What Your Results Mean

Add your roof pitch and the tool also shows how close your roof already is to ideal, so you can decide whether tilt-up racking is worth paying for. It works anywhere on Earth, north or south of the equator, including the tropics, where most calculators quietly give wrong seasonal answers.

The calculator shows six things. Each answers a different question, so read the one that matches how your panels are mounted.

All angles are measured from horizontal. A 0° panel lies flat. A 90° panel stands upright like a wall.

Example, New York City (40.7°N): recommended fixed tilt 32°, latitude rule 41°, summer 26°, winter 56°, facing true south (180°). With a 6/12 roof (26.6°), the roof sits about 5° below the recommended fixed tilt, which is close enough to mount flush.

The Best Solar Panel Angle: Short Answer

For a fixed system, the best solar panel angle is a little shallower than your latitude. Around 25–35° suits most of the US, southern Europe, the Middle East and Pakistan. Northern US states, Canada and the UK sit higher, roughly 33–40°. Face the panels toward the equator.

The gap below your latitude grows the farther you live from the equator. That’s the part most guides skip, and it’s why the next section exists.

How to Calculate Your Solar Panel Tilt Angle by Hand

You need your latitude and, for monthly angles, the sun’s declination.

Recommended fixed tilt (northern hemisphere): Tilt = 1.3793 + φ × (1.2011 + φ × (−0.014404 + φ × 0.000080509)), where φ is your latitude.

Recommended fixed tilt (southern hemisphere): Tilt = −0.41657 + φ × (1.4216 + φ × (0.024051 + φ × 0.00021828)), where φ is your negative latitude. Drop the minus sign from the answer.

Worked example for Denver at 39.7°N: 0.000080509 × 39.7 = 0.0032; −0.014404 + 0.0032 = −0.0112; × 39.7 = −0.4447; + 1.2011 = 0.7564; × 39.7 = 30.03; + 1.3793 = 31.4°.

Summer and winter tilt: take your latitude, subtract 15° for summer and add 15° for winter. Denver: 25° in summer, 55° in winter. This ±15° adjustment is the planning method documented by the USDA Natural Resources Conservation Service for fixed PV arrays. Never go below 0° or above 90°.

Monthly tilt: subtract the sun’s declination for that month from your latitude. Declination is the sun’s position north or south of the equator, swinging between +23.45° in June and −23.45° in December. The standard formula is:

Declination = 23.45 × sin(360 × (284 + n) / 365), where n is the day of the year.

Mid-month declinations and the resulting angles for three cities:

These monthly angles face the noon sun directly. *Karachi’s raw May to July values are 6°, 2° and 4°; they’re raised to 10° so rain can still wash the glass (more on that below).

Solar Panel Tilt Angle by City

Latitude rule shown for comparison. Seasonal angles are latitude ±15°. In the southern hemisphere, winter runs June to August.

*Honolulu’s raw summer figure is 6°; it’s raised to the 10° practical minimum.

London’s recommended 36° falls inside the 35–42° range the EU’s PVGIS database gives for the UK, which is a useful cross-check that the weather-based formula holds up in a cloudy climate. Not on the list? Enter your city in the calculator above.

Near the Equator: When the Summer Sun Is Behind You

Between the equator and 23.45° latitude, in the tropics, the noon sun spends part of the summer on the “wrong” side of you. In Mumbai (19.1°N), from roughly mid-May to late July, the midday sun passes slightly north of overhead. Run the monthly formula for June and you get −4°, which is the calculator’s way of saying a perfectly sun-facing panel would tip slightly north.

Most calculators either show that negative number with no explanation or clamp it to zero without telling you. Here’s what it means in practice:

• For a fixed array in the tropics, keep facing the equator at the recommended tilt. The sun sits so high for those weeks that the loss from a slight south lean is tiny.
• Don’t drop below about 10°. At very low angles rain stops washing the glass, and dust, pollen and bird droppings build a film. The small geometric gain from going flatter doesn’t make up for the soiling.
• If you adjust monthly, set the panels to 10° south-facing in the months the formula goes negative, rather than flipping the rack.

The same effect happens in reverse south of the equator, in places like northern Australia and Brazil, during December and January.

How to Measure the Tilt Your Panels Already Have

Before you change anything, find out what you’re working with. Three ways, from easiest to most precise:

1. Phone level. On an iPhone, open the Measure app and choose Level. On Android, install any free inclinometer app. Lay the phone flat on the aluminum frame of a panel (not the middle of the glass, which can flex slightly) and read the angle.
2. Digital angle finder. A magnetic digital protractor from a hardware store reads to a tenth of a degree and sticks to steel racking. It’s the tool installers use.
3. Rafter pitch, from the attic. Hold a level horizontally against the underside of a rafter, mark 12 inches along the level, and measure straight down to the rafter at that mark. That vertical distance in inches is your rise, so 6 inches means a 6/12 roof. Use the conversion table in the next section.

For flush-mounted panels, the panel tilt equals the roof angle. For panels on tilt-up legs, measure the panel itself, since the racking adds angle on top of the roof.

Flat Roofs, Snow, Dust and Bifacial Panels

Flat roofs give you freedom to pick any angle, but steeper isn’t automatically better. Each tilted row casts a shadow on the one behind it, and the steeper the tilt, the wider the gap between rows has to be. On a roof with fixed space, a lower tilt of 10–15° often fits more panels and produces more total energy than fewer panels at the ideal angle. Lower tilts also catch less wind, which matters for ballasted systems that sit on the roof without bolts. Ballast weight is a structural calculation for your installer, not a rule of thumb.

Snow slides off steep panels and sits on flat ones. In heavy-snow areas, a steeper angle around 40° or more helps panels clear themselves, at a small cost in summer output. Wet snow on a near-flat array also adds real weight to the structure underneath.

Dust and dry climates call for that 10° minimum and regular cleaning. In places like the Gulf states, Sindh and Rajasthan, where rain is rare, a steeper tilt won’t self-clean much anyway, so plan for manual cleaning rather than relying on angle.

Bifacial panels collect light on both sides, including light reflected off the ground. The rear-side gain depends on what’s underneath (white gravel and snow reflect far more than grass), panel height and row spacing. Start from the recommended tilt and check the manufacturer’s bifacial design guidance, because these factors can shift the best angle.

What a Solar Panel Tilt Angle Calculator Can’t Tell You

Every number on this page comes from your latitude and published formulas. That makes it fast and easy to check, but it leaves out things that matter for a real installation:

• Shading. A tree or chimney that blocks the array for an hour around midday costs more than a 10° tilt error. Fix shade before fine-tuning angle.
• Local weather. Formulas can’t see your microclimate, coastal fog or monsoon season.
• Exact energy output. Results are angles, not kilowatt-hours. For production estimates, enter your address, tilt and azimuth into PVWatts (US-focused, free) or PVGIS (worldwide, free).
• Structure and codes. Roof load, wind uplift, fire setbacks and permits need an installer or engineer.
• Panel temperature, wiring and inverter losses. None of these depend much on tilt, and none are modeled here.

Use the calculator to set a target and sanity-check a quote. Use a site-specific model before you buy racking.

Frequently Asked Questions