Rain to Snow Conversion Calculator

The classic rule of thumb is 10:1 — one inch of rain (liquid water) makes about ten inches of snow. It works best when the temperature is near freezing (roughly 28–34°F / −2–1°C). Away from freezing, the real ratio can be half or triple that, which is why this calculator also offers a temperature-adjusted mode.

Temperature is the main driver. Near freezing, snow is wet and dense (around 10:1 or lower). As it gets colder, crystals grow drier and fluffier, so the ratio climbs — 15:1, 20:1, even 30:1 or more. Humidity, crystal shape, and wind also matter: two storms at the same temperature can still produce different snow.

The Kuchera method was developed by U.S. Air Force meteorologist Evan Kuchera and is used on operational forecast maps. Instead of a fixed 10:1, it adjusts the snow-to-liquid ratio using the warmest temperature in the atmospheric column, accounting for melting or mixing when temperatures are near freezing. It is an improvement over a static ratio, but it ignores the dendritic growth zone and can overestimate in marginal near-freezing regimes and in very cold air. This calculator's temperature-adjusted mode applies the same temperature-adjustment idea using surface temperature and the published FAA/NWS conversion table.

The highest ratios come from moderately cold air, roughly 15°F down to 0°F (−9 to −18°C), where ice crystals grow into large, airy dendrites that pile up deep. If air gets extremely cold (below about 10°F), ratios can actually fall again because very cold air holds less moisture, so flakes stay small. The FAA table used here tops out at 50:1 to 100:1 for very cold bands — treat those as upper-bound estimates.

Divide the snow depth by the ratio. For example, 30 inches of snow at a 30:1 ratio melts down to 1 inch of liquid water. Switch this calculator to Snow → Rain mode and it applies the same temperature bands in reverse.

Lake-effect snow forms when frigid air flows over relatively warm lake water, producing intense, narrow snow bands. It is famously fluffy, with above-average ratios. Because it is driven by local lake processes rather than temperature alone, generic conversion tables tend to understate it — for a lake-effect event, trust your local National Weather Service forecast over any ratio calculator.

Yes. Wet snow can reach the ground with surface temperatures a degree or two above 32°F if the air aloft is cold enough; the flakes partially melt on the way down, making heavy, low-ratio snow. This calculator flags surface temperatures above 34°F as rain, since sustained snow becomes unlikely.

Trained observers measure on white snow boards during the storm — ideally every hour, clearing the board each time — because snow settles and can melt between measurements. A single measurement after the storm ends usually undercounts the true total. Liquid equivalent is found by melting a core sample of the snow.

Fresh fluffy snow settles under its own weight, and wind plus partial melting compact it further. Snow that fell at a 20:1 ratio can lose a large fraction of its depth within a day. Convert freshly measured depths for the most accurate liquid equivalent.

No. Sleet (ice pellets) are raindrops that refroze into nearly solid ice, and freezing rain is liquid — both are far denser than snow. Snow-to-liquid ratios only apply to snow.

The DGZ is the atmospheric layer between about −12°C and −18°C where ice crystals grow into branching dendrites. When this layer is deep and has strong upward motion, flakes clump into large aggregates that trap lots of air — the recipe for very high snow ratios. The Kuchera method does not model the DGZ, which is one of its known limitations.

It is a planning-grade estimate. The temperature-adjusted mode uses only surface temperature and the operational FAA/NWS conversion table; real storms also depend on humidity, crystal type, wind, and the temperature profile aloft. Expect the true ratio to land within a few points of the estimate for ordinary snowstorms, and always check official forecasts for a real event.

At the standard 10:1 ratio, 1 mm of rain makes 10 mm — exactly 1 cm — of snow, and 1 inch of rain makes 25.4 cm of snow. This calculator converts units for you: enter rain in inches or millimeters and read snow in inches or centimeters.

Liquid equivalent — snow water equivalent (SWE) when measured in a snowpack — is the depth of water you would get by melting the snow completely. It equals snow depth divided by the snow-to-liquid ratio, and it is the number hydrologists and forecasters actually care about.

Wind does not change the liquid equivalent, but it redistributes the snow. Ten inches of forecast snowfall can drift to two feet against a fence and leave nearby pavement nearly bare. Reported storm totals are measured in sheltered spots to avoid drift bias.

Climatological averages in much of the United States cluster around 10:1 to 12:1, but any single storm can range from about 6:1 (wet coastal snow) to 30:1 or more (cold powder). The “average” describes climate, not your storm — which is exactly why temperature-adjusted ratios exist.