# This Calculator Tells You If A ‘Discount’ Is Worth It

It certainly feels like everything is on sale all the time these days. But not all sales are created equal. It’s especially important to recognise this during the holidays, when shopping holidays feature complex discount schemes that sometimes carry equally complex limitations.

If mental maths isn’t your strong suit, check out the Black Friday Calculator. “A lot of these seemingly genuine sales are often maths traps,” said Hanna Pamula, a Ph.D. student in Poland who built it for The Omni Calculator Project. She includes nine different discount scenarios —per cent off, buy-one-get-one, and a discount for buying multiple items, to name a few—to help you determine whether a discount is worth your time and money.

While the calculator is named with Black Friday in mind, you can use it any time you want to check the maths on a supposed sale price.

To kick the tires on this calculator, I tested out a simple “20% off everything” sale at shoe retailer DSW. I entered the original price of \$US69.99 (\$102) for a pair of sneakers, the discount of 20%, and the additional tax of 7% I’d pay. The calculator determined a savings of \$US14.98 (\$22), with a gif of a snoozing Garfield asking me if it’s worth getting out of bed.

I could have gone through the steps of adding the item to my cart, entering my shipping info to determine tax, and adding the promo code. But let’s face it: by that point, I probably would have clicked the extra two buttons to buy the shoes.

But that’s an easy one. Let’s try something a little more complex. The calculator can crunch the following discount scenarios:

• % off

• % off on a second or third product

• 2 for 1

• 3 for 2

• 4 for 3

• Double or triple discount (Ex: 50% off+ 30% off)

• Discount on multiple units

How about a buy one, get one 50% off sale? I checked out the sale online at Shoe Carnival (I didn’t mean to make this a battle of the discount shoe stores, but here we are) to test the calculator’s BOGO feature. I need a pair of snow booties for next winter, of course, and it’ll cost me \$146. But if the second item is 50% off, maybe I’ll get a pair of Doc Martens. Is it a good deal?

The calculator tells me I’ll save just over \$70. For two pairs, I’ll pay just 23.7% of what I’d pay for both pairs at full price. Of course, the best way to save is to buy only the pair I truly need. But if your shopping list includes more than items for your own material self, doing the maths can help you maximise your budget.

One thing to watch out for as you start comparing holiday sales is price inflation. We’ve written about this before: In the weeks leading up to a big sales event, it’s a common practice for retailers and merchants to increase their prices slightly so whatever discount they offer later seems even better. (This is something Kogan recently got in strife for by the ACCC.)

[referenced url=”https://www.lifehacker.com.au/2019/05/the-accc-just-tore-kogan-a-new-one/” thumb=”https://www.lifehacker.com.au/wp-content/uploads/sites/4/2019/05/Kogan2-410×231.jpg” title=”The ACCC Just Tore Kogan A New One [Updated]” excerpt=”The Australian Competition and Consumer Commission (ACCC) is taking Kogan to Federal Court for alleged false and/or misleading advertising. The ad in question was a 10% discount promotion which ACCC claims is in breach of the Australian Consumer Law. Here are the details.”]

“Retailers will do anything to draw your attention and make deals look better than they really are,” Pamula said by email. Combine a little advance research with some mathematic reinforcement, and you’ll be in a good position to spend wisely without getting snookered by a bad deal.