What Is the Rain to Snow Calculator?
This tool converts a given amount of rainfall — or the liquid-equivalent of precipitation — into an estimated depth of snow. It uses the snow-to-rain ratio, which tells you how many inches of snow form from one inch of liquid water. The most commonly quoted average is 10:1, but the real ratio swings widely with air temperature, from roughly 5:1 for wet, heavy snow near freezing to 20:1 or more for dry powder in very cold air.
How to Use It
Enter the rainfall (or melted precipitation) in inches, then pick the snow-to-rain ratio that best matches the conditions. If you are unsure, the default 10:1 is a solid all-purpose estimate. The calculator multiplies the two values and returns the expected snow depth.
The Formula Explained
The equation is simply $$\text{Snowfall} = \text{Rainfall} \times \text{Ratio}$$ The ratio captures how "fluffy" the snow is: colder air produces lighter, more voluminous flakes (higher ratio), while temperatures near 32°F yield dense, slushy snow (lower ratio). Because the calculation is linear, doubling the ratio doubles the predicted snow depth.
Worked Example
Suppose a storm drops 0.5 inches of liquid precipitation and the air is cold and dry, supporting a 15:1 ratio. The snowfall estimate is $$0.5 \times 15 = 7.5 \text{ inches}$$ of snow. Had the storm been warmer at a 10:1 ratio, you'd expect only 5 inches.
FAQ
Is 10:1 always accurate? No — it is an average. Cold, dry storms can exceed 20:1, while warm, wet storms may be 5:1 or even less.
What rainfall value should I enter? Use the liquid-water equivalent of the precipitation. If a forecast gives expected rain that would otherwise fall as snow, use that number.
Can I reverse the calculation? Yes — to find liquid equivalent from snow depth, divide the snowfall by the ratio.
