How it works
The formula
salt each time (lb) = area × 4 ÷ 1,000
bags = salt each time × times a winter ÷ 50, rounded up
Assumptions
- 4 lb per 1,000 sq ft is the most Minnesota's Pollution Control Agency recommends for each application, as cited by the League of Minnesota Cities. Wisconsin Salt Wise puts it as one 12 oz coffee mug of salt for about 10 sidewalk squares. Many bag labels suggest much more; the extra mostly washes into lawns, drains and streams.
- You shovel or plow first. Salt is for the thin layer that's left, not for melting snow.
- Rock salt (sodium chloride) works down to about 15°F. Colder than that, calcium or magnesium chloride melts ice, or sand gives grip without melting.
- Rock salt comes in 50 lb bags, typically $10–$16 a bag (checked Oct 2026).
Worked example
A 20 × 20 ft driveway and a 30 × 4 ft walk, salted 12 times
- Area: 400 + 120 = 520 sq ft
- Each time: 520 × 4 ÷ 1,000 = 2.08 lb
- Winter: 2.08 × 12 = 25 lb, so 1 bag of 50 lb
Salt for common areas
| Area | Each time | 12 times | 20 times |
|---|---|---|---|
| Front walk and steps, 200 sq ft | 0.8 lb | 1 bag | 1 bag |
| 2-car driveway (20 × 20 ft), 400 sq ft | 1.6 lb | 1 bag | 1 bag |
| Driveway and walk, 600 sq ft | 2.4 lb | 1 bag | 1 bag |
| Long driveway, 1,000 sq ft | 4 lb | 1 bag | 2 bags |
Questions people ask
How much salt should I put on my driveway?
No more than about 4 lb per 1,000 sq ft each time, after shoveling: about 1.6 lb for a 20 × 20 ft two-car driveway. That's roughly a coffee mug or two, spread so the grains are about 3 inches apart. More salt doesn't melt ice faster; it just ends up in the grass and storm drains.
How many bags of rock salt do I need for a winter?
For a 20 × 20 ft driveway and a front walk salted 12 times, one 50 lb bag at the recommended rate. If you salt the way many bag labels suggest, you'd use several times that.
Does rock salt work in very cold weather?
Not well. Rock salt slows down a lot below about 15°F. For colder days, calcium chloride or magnesium chloride melts ice at lower temperatures, and sand or grit gives traction without melting anything.
Will rock salt damage my concrete?
It can, especially new concrete (less than a year old) and concrete that's flaking already, because salt water soaks in and freeze-thaw cycles break the surface. Use as little as works, sweep up leftovers, and avoid salting fresh concrete; sand is safer there.
Is rock salt safe for pets and plants?
Salt irritates paws and harms grass and shrubs along the edge of the drive. Use less, keep it off the lawn, wipe pets' paws, and sweep up the leftover salt once the pavement is dry; it can be reused next time.