Albedo describes how much sunlight a surface bounces back into space versus absorbs — a single number from 0 to 1 that explains why snowfields stay cold, why asphalt gets scorching hot, and why painting a roof white can meaningfully cut cooling costs. This calculator computes albedo directly from measured radiation, or from a reference table of typical values for common natural and built surfaces.
How the Surface Albedo Calculator works
Albedo is simply reflected radiation divided by incident radiation: albedo = reflected / incident. Both values need to be in the same units — typically watts per square meter (W/m²) from a pyranometer measurement, or any consistent solar radiation unit. The result is a dimensionless fraction between 0 and 1, often also expressed as a percentage.
If you don't have measured radiation values, the Material Lookup mode uses published reference values (midpoints of the commonly cited ranges from NASA Earth Observatory and NOAA climate resources) for surfaces like fresh snow, forest canopy, desert sand, concrete, asphalt, and reflective roofing.
Inputs and what they mean
Reflected radiation is the portion of incoming sunlight bounced back off the surface, measured with the same instrument and in the same units as incident radiation.
Incident radiation is the total solar radiation striking the surface before any of it is reflected or absorbed — this must be a positive value, since albedo is undefined when there's no incoming radiation to reflect.
Material (lookup mode) selects a typical published albedo value. Real-world albedo for any given material varies with sun angle, moisture content, surface age, and cleanliness — a wet or aged surface often has a noticeably different albedo than a fresh, dry one of the same material.
Limits and edge cases
This calculator computes a single-point (broadband) albedo estimate. It does not account for spectral albedo (how reflectivity varies by wavelength), the bidirectional reflectance distribution function (how albedo changes with sun and viewing angle), or seasonal and diurnal variation. Material lookup values are reference midpoints, not site-specific measurements — a real survey or remote-sensing dataset will always be more accurate for a specific location.
The heat-island absorbed-energy comparison is a simplified illustration of the physical relationship between albedo and absorbed solar energy; it does not model atmospheric effects, surface emissivity, convective cooling, or the many other factors that determine actual surface temperature.