Ice Melt Calculator

How to estimate ice melt

Ice melt bags tell you to use far more than winter-maintenance programs say a driveway needs. The rate winter-maintenance programs give homeowners is small enough to measure with a coffee mug. The math is one multiplication.

salt per application = rate per 1,000 sq ft × (paved area ÷ 1,000)
salt for the winter = salt per application × number of applicationsUniversity of Minnesota LTAP: "apply about 1 pound of salt per 250 square feet" and "use no more than 4 lbs. of salt per 1,000 square feet."

Measuring what you treat

Measure the driveway and the walk as rectangles and add them. A two-car driveway is often around 20 by 24 feet, or 480 square feet. A 4 foot walk to the door adds 4 square feet for every foot of length. Add the front steps if you salt them.

Count only what you actually treat. Say you clear the whole driveway but only salt the tire tracks and the path to the door. Then the area is the tracks and the path. That alone can halve the answer.

The rate

The University of Minnesota's Local Technical Assistance Program puts it plainly in its winter salt guide for homeowners. Use about 1 pound of salt per 250 square feet. That is 4 pounds per 1,000, and it is also the most to use. Wisconsin Salt Wise gives a range of 1 to 4 pounds per 1,000 square feet.

Their way of picturing it is more useful than the number. A 12-ounce coffee mug holds about a pound of rock salt. One mug covers ten sidewalk squares or a 20 by 12 foot driveway. Scattered properly, the crystals land about 2 to 3 inches apart.

Why the bag says more

Compare that with the manufacturers. OxyChem recommends 28 pounds of its Peladow calcium chloride per 1,000 square feet. Morton says a 12 pound jug of Action Melt Elite covers about 355 square feet, which is roughly 34 pounds per 1,000. The Minnesota guide expects this and says package rates will work but are likely higher than needed in most cases.

On the 640 square foot drive and walk this page opens with, the Minnesota rate is 2.6 pounds per application. The Peladow rate is 17.9 pounds. Same pavement, seven times the salt.

A source that disagrees, and why we did not use it

The Minnesota Pollution Control Agency's winter press releases use the same coffee mug, the same 20-foot driveway and the same 10 sidewalk squares. Then they add "about 1,000 square feet" in brackets. That figure does not match its own examples. Ten 5 by 5 foot sidewalk squares are 250 square feet, and a 20 by 12 foot driveway is 240. The university guide uses the same examples and says 250. The arithmetic supports 250, so that is the figure used here.

Temperature decides the product

Rock salt is sodium chloride, and it slows down sharply in hard cold. Wisconsin Salt Wise says salt becomes less effective below 15°F, measured at the pavement. Bags often print a lower number, such as Morton's 5°F. That is closer to the limit of what salt can do at all. On a sidewalk, in a reasonable time, it stops working sooner.

Below 15°F, calcium chloride is the usual answer. Salt Wise puts its working range down to -20°F. The Minnesota guide adds that a blend with calcium or magnesium chloride may let you use even less. The rate on this page is written for rock salt, so treat it as the upper end for a chloride blend.

The winter total

One application is the number the guidance gives. The winter is what you buy. Nobody publishes a typical count, because it depends on where you live and how many storms arrive. This page asks for your number. Last winter's storm count is a reasonable start.

At 2.6 pounds a time and 8 applications, the 640 square foot example needs about 20 pounds for the season. One 25 pound bag covers it with a few pounds spare. Rock salt keeps from one winter to the next if it stays dry. A bigger bag than you need is rarely wasted, only paid for early.

A quick cost check

At $10 for a 25 pound bag, the Minnesota rate costs $10 for the whole winter on that example. Now use a bag rate of 28 pounds per 1,000 square feet. The same 8 applications take about 143 pounds. That is six 25 pound bags, or $60 at the same price. The price field above is yours, so the arithmetic follows your store's numbers.

The surface underneath

Every deicer maker we read warns against the same surfaces. Compass Minerals says to use its products only on good-quality, air-entrained concrete more than one year old. It also warns against stamped, precast, cracked or weathered concrete, and against stone, brick and mortar joints. OxyChem and Cargill say the same about first-year concrete and masonry.

The concrete industry agrees on new concrete. The National Ready Mixed Concrete Association's guidance on scaling says to avoid deicing chemicals on newly placed concrete and use clean sand for traction. It also says never to use ammonium nitrate or ammonium sulfate as a deicer, because they attack concrete chemically.

Common estimating mistakes

• Following the bag rate. The Minnesota guide says package rates are likely higher than needed. The gap is seven or eight times.
• Salting before shoveling. Salt goes on the thin layer the shovel leaves. On deep snow it mostly turns to slush.
• Using rock salt in hard cold. Below 15°F at the pavement, more salt does not help. A different product does.
• Treating the whole drive when only the paths get walked. Measure only the parts you treat.
• Leaving the leftovers. Crystals still on dry pavement can be swept up and used next storm. Left there, they wash into the lawn.

When to hand it off

This page sizes the salt for a home driveway and walk. Two things fall outside it. The first is damaged concrete: flaking, scaling or a surface that is breaking up. Have a concrete contractor look at it before another winter of deicer goes on, because the concrete industry ties heavy deicer use to more scaling. The second is a business, a shared lot or a long private road, where a fall is a liability question. There, hire a winter-maintenance contractor trained in a program like Minnesota's Smart Salting.