Formula: (Product Cost * Price Markup Percentage) + Product Cost = Your Selling Price
For example, the product that you want to source from Aliexpress is sold at $5. Your price markup is 250% so you could also cover the possible shipping cost or tax fee and still get a profit. If we'll apply price markup calculation here, that would be - ($5 * 250%) + $5 = $17.50
This means that you sell the item for $17.50 at your store.
In order to calculate your profit, the quickest way to do that is to make sure you deduct the total amount that you will pay at AliExpress or other supported sites from your selling price.
That said, if the product cost is $5 and charges for shipping and tax are $4 - you'll be paying $9 all in all. Computation of the profit will be $17.50 - $9 = $8.50
Your profit from selling the item will be $8.50.
Compare at Price Markup
Formula: (Your Selling Price * Compare At Price Markup %) + Your Selling Price = Your Regular Full Price
Let's use the same amounts in the example above. Your selling price is $17.50 and you set your Compare At Price Markup to 50%. Applying the Compare At Price Markup calculation here will be ($17.50*50%) + $17.50 = $26.25
So your regular full price (compare at price) for this item will be $26.25. This is usually crossed out to show that this product in your store is on sale. And it's right beside your selling price which is $17.50.
This will let your buyer know that he can get a discount when he buys this item you put on sale.
This is an example of compare at pricing that is crossed out.
Here is a markup calculator to help the math-challenged people: