How much salt is enough?
More salt does not melt ice faster; it washes into soil, streams and groundwater, damages concrete and plants, and harms pets’ paws. Guidance from snow and ice programs such as Wisconsin Salt Wise is that about 1 pound of rock salt covers 250 square feet, or 4 lb per 1,000 sq ft. A 12 oz coffee mug holds about a pound.
The calculation
Salt per treatment = area × application rate × condition factor
Salt per winter = salt per treatment × number of treatments
The calculator uses 4 lb per 1,000 sq ft for rock salt and 3 lb for magnesium or calcium chloride, which work at lower temperatures. Light frost or preventive spreading takes about half the rate; thick ice or freezing rain about double.
Example
A 1,000 sq ft driveway and walk treated 20 times a winter with rock salt needs 4 lb per treatment and 80 lb per winter: two 50 lb bags, about $24.
Which deicer for which temperature?
| Product | Practical lowest temperature |
|---|---|
| Rock salt (sodium chloride) | about 15 °F |
| Magnesium chloride | about 5 °F |
| Calcium chloride | about −20 °F |
Below its practical temperature, a product works too slowly to be worth spreading. Use sand or grit for traction instead; they do not melt ice but make it less slippery.
Use less, get better results
- Shovel first. Salt is for the thin layer that remains, not for melting inches of snow.
- Spread evenly, with gaps of about 3 inches between grains; a handheld spreader helps.
- Pre-treat before a storm with a lighter dose or a brine, so snow does not bond to the pavement.
- Sweep up leftovers after the pavement dries and reuse them.
Protecting concrete and plants
New concrete (less than a year old) is especially vulnerable to deicers. Products labeled pet-safe or plant-safe usually contain magnesium chloride, calcium magnesium acetate or urea, and cost more. Keep salt piles off lawns and away from tree roots.