Grind vs Blast Crossover Calculator
Price grinding the whole floor against blasting the open field and grinding the edges, on your own rates, and find how much open floor blasting needs before it pays for itself.
Which Prep Route Is Cheaper on This Floor
Shot blasting is faster per square foot and carries a mobilization charge a grinder does not. That gives it a crossover rather than a verdict: below some amount of open floor the fixed cost dominates and grinding wins, above it the production rate dominates and blasting wins. Where that point sits depends on your rates, your machines and how open the floor is, so this tool seeds no prices at all. Enter the floor, the two machines and your own four costs, and it prices both routes and tells you how much drivable floor blasting needs before it pays for itself.
The Floor
Area and perimeter, because the edges are what a blaster cannot reach.
The Machines
The blast rate is derived from path width and walking speed, not looked up.
Your Costs
Nothing here is pre-filled. The crossover is only as good as these four numbers.
Enter a floor area, a perimeter and your crew rate to compare the two routes.
This is a cost comparison and not a method recommendation. Cost is one input among several and it is often not the deciding one: dust sensitivity in an occupied building, a soft slab the blaster can overshoot, or a coating that smears rather than shatters can each settle the method on their own, whatever the arithmetic says. Both routes assume sound, dry, degreased concrete and a grinder already on site, so the grinder’s own mobilization appears in neither figure, because it is in both routes and cannot change which one wins.
How the Grind vs Blast Crossover Calculator Works
- Choose Imperial (ft²) or Metric (m²), then enter the whole floor area and its perimeter
- Set the edge band your blaster cannot reach, from the machine spec sheet, which decides how much of the floor is edge
- Check the two production figures: your grinding rate per pass, and the blast path width and speed the blast rate is derived from
- Enter your own four costs: crew rate, grinding cost per unit area, abrasive per hour, and the blaster mobilization
- Read which route is cheaper on this floor, and how much open field blasting needs to break even
Examples
Frequently Asked Questions
Why does the break-even figure ignore the edges?
Because the edges cost exactly the same in both routes, so they cannot decide between them.
A shot blaster cannot reach a wall, a corner, or anything it cannot drive under, so the perimeter strip is ground either way. That means the edge cost appears identically on both sides of the comparison and cancels out of it entirely. What is left is the open field, which is the only part where the two routes actually differ: the grinder covers it slowly and cheaply per hour, the blaster covers it fast but has to pay off a mobilization charge first.
So the break-even the tool reports is an amount of open field, not a floor size. Two floors of the same area with very different perimeters have very different answers, which is why the tool asks for the perimeter rather than assuming a shape.
Why are none of the costs pre-filled?
Because a crossover computed from our numbers would tell you where the break-even sits for a contractor who does not exist.
Every figure in this comparison is one we would have to invent: what a crew costs you an hour, what your tooling and power come to per square foot, what steel shot costs where you buy it, and what a blaster costs to get to site in your area. Our methodology page commits to not publishing market rates we cannot defend, and four of them stacked into a single verdict is exactly the kind of number that commitment exists to exclude.
The two figures that are pre-filled are production rates rather than prices, and both are shared with the calculators they came from: the grinding rate is the Grinding Time calculator, and the blast speed is the Shot Blast Production calculator, where the blast rate is derived from path width and walking speed rather than looked up.
Where do I get the grinding cost per square foot?
From the Concrete Grinding Cost Calculator, which exists to produce exactly that figure. It takes what you paid for the machine and the tooling, your power source, and your servicing intervals, and returns a cost per square foot covering tooling wear, power, depreciation and servicing.
Enter that number here without labor in it. This tool applies your crew rate separately, to both routes, because the hours differ between them and the rate does not. Adding labor to the per-area figure as well would count it twice on the grinding side and tilt the comparison toward blasting.
Does the cheaper route mean I should use it?
No, and the tool deliberately does not say so. This is a cost comparison, not a method recommendation.
Several things settle the method on their own regardless of the arithmetic. A soft or friable slab is where a blaster can overshoot the profile you wanted. A soft or thick existing coating smears under abrasive rather than shattering, which loads the machine up. An occupied building can make dust the deciding factor whichever way the money points. And an abrasive recovery system does not like a damp or oily floor, so a contaminated slab has to be degreased before either method.
Use this to find out what the choice costs you, then read grinding vs shot blasting for the six questions that decide it on site.
What does the mobilization figure need to include?
Everything one-off about getting the blaster onto the job and off it again: delivery and collection, any hire minimum you cannot avoid, and the time to set up and test a strip before the production run starts.
It is the single most important number in the comparison, because it is the whole thing the open field has to pay back. The break-even scales directly with it: double the mobilization and you double the amount of drivable floor blasting needs before it makes sense.
The grinder is assumed to be on site in both routes, so its own mobilization is in neither figure. That is not an omission. A cost that appears identically in both routes cannot change which one wins, in exactly the same way the edges cannot.
Why does it sometimes say blasting never wins?
Because at the rates you entered the blast route costs more per square foot of open field than grinding does, so there is no saving to pay the mobilization back with. When that happens no floor is large enough, and the tool says so rather than quoting a break-even that grows to infinity.
It usually means one of two things. Either the abrasive and hourly hire are genuinely high where you are, or the blast rate is lower than it should be because the path width or the travel speed is set wrong. The derived blast rate is shown next to those two fields precisely so you can sanity check it: a 15 in path at 10 ft per minute is 750 ft² an hour, which is roughly two and a half times a typical grinder.
Important Notes
- No price is seeded anywhere in this tool. The two pre-filled production figures are shared with the Grinding Time and Shot Blast Production calculators, so none of the three can drift from the others.
- The blast rate is derived from path width and travel speed rather than looked up, which makes it geometry rather than a claim about the trade.
- The edge band is an example value taken from a machine spec sheet, not an average. Read your own machine.
- Both routes assume sound, dry, degreased concrete and a grinder already on site. The grinder mobilization is in both routes and therefore in neither figure.
- Passes apply to both routes equally, so they scale the comparison rather than tilting it.
- Cost is one input among several and often not the deciding one. A soft slab, a smearing coating or an occupied building can settle the method whatever the arithmetic says.