Key takeaways
- A 12-ounce coffee mug of salt treats about a 20-foot driveway or 10 sidewalk squares.
- Scatter it with space between the grains. Piles do not melt faster.
- Clear first, then salt. Salt on top of unplowed snow is mostly wasted.
- Below about 15°F pavement temperature, rock salt stalls. Switch products or use sand.
On this page
The coffee-mug rule
Wisconsin's Salt Wise program, run with the state Department of Natural Resources, puts it simply: one 12-ounce coffee mug of salt is enough to treat an entire 20-foot driveway, or about 10 sidewalk squares. Scatter it so there is space between the grains.
That surprises most people, who are used to pouring salt until the pavement looks white. It works because salt does not need to cover the ice. It needs to start melting, and the brine it makes spreads out and does the rest.
Why more salt does not work faster
Salt melts ice by dissolving into brine, which has a lower freezing point than water. Each grain bores down and spreads outward. Once there is enough brine to break the bond between ice and pavement, extra salt adds nothing. It sits on top, gets tracked inside, and washes into the lawn and the storm drain at the next thaw.
Overapplying costs you twice: once for the salt, and again for the damage it does to grass and shrubs, to concrete and to pets' paws.
Clear first, then treat
Salt is for the thin layer the shovel or plow leaves behind, not for the snow itself. Salting on top of three inches of snow means melting three inches of snow into slush, which then refreezes. Clear the snow, then treat what is left, and focus on the spots that matter: steps, walking paths, the slope and the apron.
Temperature decides what works
Rock salt slows badly as pavement temperature falls below about 20°F and stops being useful near 15°F. Pavement is often colder than the air on clear nights and warmer on sunny afternoons, which is why the same salt works at 2 p.m. and does nothing at 6 a.m.
| Product | Practical working limit (pavement) | Notes |
|---|---|---|
| Rock salt (sodium chloride) | about 15°F | Cheapest; stalls in deep cold |
| Magnesium chloride | about 5°F | Gentler on concrete; costs more |
| Calcium chloride | about −20°F or lower | Works in deep cold; use sparingly |
| Sand or grit | any temperature | Traction only; melts nothing |
Practical field limits, not laboratory eutectic points. Manufacturers sometimes quote lower numbers.
How to spread it
- A hand-held spreader gives a far more even scatter than a scoop.
- Aim for visible gaps between grains, not a white coat.
- Treat before a freeze when you can. A small amount on bare pavement ahead of freezing drizzle keeps ice from bonding at all. See anti-icing.
- Sweep up leftover dry salt after the ice is gone and reuse it.
For parking lots
Commercial lots use calibrated spreaders and application rates adjusted for pavement temperature, the type of precipitation and whether the surface was pre-treated. The principle is the same as at home: the right amount at the right time works better than more. Commercial treatments should also be logged, with the product and the time. See snow logs.
How we handle salt
We quote salting separately from plowing, so nobody pays for salt the weather made useless. We match the product to the temperature, and when it is too cold for salt to do anything, we say so instead of billing for it.
Sources
- Wisconsin DNR: reduce your salt use this winter — a 12-ounce coffee mug treats about a 20-foot driveway
- Minnesota Stormwater Manual: how salt works and deicing chemicals — practical working temperatures
Written by the Macomb Lawn & Snow Solutions team in Macomb Township, Michigan. We plow and salt homes and businesses across all 26 Macomb County communities, November 15 to April 15. Published September 28, 2026. About us · How we research these guides · How our dispatch works