The Burger King is known for his football moves, but he could take up hockey soon.

Burger King Worldwide will acquire Tim Hortons, the Canadian fast-food chain famous for its coffee and doughnuts. The deal, announced this week and estimated to be worth about $11 billion, means Burger King will do a tax inversion — that is, change its domicile to Canada and, potentially, save on corporate income taxes.

How much would this save Burger King in taxes? And what would the Whopper equivalent of those savings be? Using Burger King’s and Tim Hortons’ 10-K filings, we can do a back-of-the-envelope calculation.

In 2013, Burger King’s effective corporate income tax rate was 27.5 percent; Tim Hortons’ was 26.8 percent. These tax rates fluctuate over time and could change after the deal is finalized. Executives at the two companies claim the main purpose of the deal is not just to lower tax rates. But according to The New York Times, Burger King would “shave only a couple of percentage points” through this inversion, “people briefed on the deal negotiations” said.

So, let’s assume (and this is just an educated guess) “a couple of percentage points” to be 2.5 percentage points. Taking Burger King’s 27.5 percent effective tax rate, we’ll estimate that the effective tax rate in the near future will be 25 percent. In 2013, Burger King’s income before taxes totaled $322.2 million. That means a theoretical tax savings of $8.1 million.

What’s the Whopper equivalent of $8.1 million? Hack the Menu’s estimate puts the price of a single Whopper at $3.49. And let’s assume the profit gained from the sale of the marginal Whopper is equivalent to the gross profit margin (that’s total sales minus the direct costs of producing Whoppers). Burger King’s 2013 gross profit margin is oddly large (74.6 percent) due to idiosyncratic accounting factors. So instead, let’s use comparable estimates from similar companies. If we average across three competitors (McDonald’s, Wendy’s and Jack in the Box), we get a 27.4 percent gross profit margin. This means Burger King gets about 96 cents profit for each Whopper sold.

Thus, the $8.1 million in tax savings is equivalent to the profit from selling about 8.4 million Whoppers.

But what if there were a backlash against Burger King for moving its headquarters to Canada? What if Americans refused to buy its burgers and fries? For the company to be better off after the tax inversion, its estimated tax savings need to be greater than any potential drop in sales.

Think of the after-tax gain like this: Burger King keeps 72.5 cents for every dollar earned in the U.S. In Canada, it’ll get 75 cents per U.S. dollar. So, sales would need to drop 3.5 percent to wipe out any tax savings.

Burger King’s revenues worldwide were just over $1.1 billion in 2013, and about $604 million came from U.S. sales, according to the company’s 10-K. So, a decline of 3.5 percent in Burger King’s overall revenues is nearly $40 million. In that case, total sales in the U.S. would need to drop 6.5 percent.