Snow to Rain Ratio Calculator
With a snow to rain ratio of 10:1, 10 inches of snow hold 1 inch of liquid water. The National Weather Service calls 10:1 typical but notes it is right only about 25 % of the time, so you can enter any ratio here.
Example: Convert: Snow → water · Amount 10 · Unit: inches · Snow to liquid ratio 10 : 1 → Result: 10 in of snow ≈ 1 in of water at 10:1. Source: National Weather Service Nashville, Weather 101 – Winter Weather (C. Mueller), slides 36–37 “Snow Ratios”: typical 10:1, correct about 25 % of the time, observed 3:1 to 100:1; 6:1 heavy wet, 11:1 local average, 30:1 very light (read 10.10.2026). Updated: .
How it is calculated
Water = snow ÷ ratio, and the other way around, snow = water × ratio. The snow ratio tells you how much liquid water is in fresh snow. The NWS office in Nashville explains it this way: “If 10 inches of snow occurs, 1 inch of liquid water is contained within the snow.”
10 inches of snow at different ratios
| Ratio | Snow | Water |
|---|---|---|
| 6:1 | 10 in | 1.67 in |
| 10:1 | 10 in | 1 in |
| 11:1 | 10 in | 0.91 in |
| 20:1 | 10 in | 0.5 in |
| 30:1 | 10 in | 0.33 in |
Which ratio should I use?
According to the NWS, 10:1 is the ratio you hear most, but it is correct only about 25 % of the time. Observations of fresh snow range from 3:1 up to 100:1, and the temperature profile of the atmosphere has a big impact. The same NWS presentation describes 6:1 as heavy, wet snow, 11:1 as about average for its own area (Nashville), and 30:1 or more as very light snow you can brush away with a broom.
- Use your local forecast’s ratio if it gives one.
- One inch of water on 1,000 square feet is about 623 gallons (1 gallon = 231 cubic inches).
- For metric amounts switch the unit to cm; the ratio stays the same.
Convert inches and centimeters with the inch to cm converter; how much rain a roof collects in a year shows the rainwater harvesting calculator.
Frequently asked questions
What is the typical snow to rain ratio?
The NWS calls 10:1 typical: 10 inches of snow melt to 1 inch of water. It notes this is correct only about 25 % of the time.
How much water is in 10 inches of snow?
About 1 inch at 10:1, 1.67 inches for heavy wet snow at 6:1 and 0.33 inches for light snow at 30:1.
How much snow would 1 inch of rain be?
At 10:1 about 10 inches; at 20:1 about 20 inches. Choose “Water (rain) → snow” and enter your ratio.
Why does the ratio change?
It depends on how much water the snow holds. The NWS says the temperature profile of the atmosphere has a big impact; ratios of 3:1 to 100:1 have been observed.
How many gallons of water are in an inch of snow on my roof?
Divide the snow by the ratio, then multiply inches of water by the area in square feet, 144 and divide by 231. At 10:1, 1 inch of snow on 1,000 ft² is about 62 gallons.
Sources and legal basis
- National Weather Service Nashville, Weather 101 – Winter Weather (C. Mueller), slides 36–37 “Snow Ratios”: typical 10:1, correct about 25 % of the time, observed 3:1 to 100:1; 6:1 heavy wet, 11:1 local average, 30:1 very light (read 10.10.2026)
- NIST SP 811, Appendix B.8: 1 in = 2.54 cm, 1 gallon (U.S.) = 3.785 412 L, 1 in³ = 1.638 706 E-05 m³, so 1 gallon ≈ 231 in³ (read 10.10.2026)
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