Blog
Practical guides that explain the formulas behind our calculators, with worked examples.
How Much Does Etsy Take Per Sale? Etsy Fees Explained
Read article: How Much Does Etsy Take Per Sale? Etsy Fees ExplainedA line-by-line look at Etsy’s listing, transaction, payment processing and Offsite Ads fees, with worked examples on four sales.
How to Calculate Rafter Length: Formula, Factors and Examples
Read article: How to Calculate Rafter Length: Formula, Factors and ExamplesCalculate rafter length from rise and run, or from a pitch with a simple factor. Includes a factor table and worked examples.
How Many Bags of Concrete in a Cubic Yard? 40, 60 and 80 lb Bags
Read article: How Many Bags of Concrete in a Cubic Yard? 40, 60 and 80 lb BagsA cubic yard of concrete is about 90 bags of 40 lb, 60 bags of 60 lb or 45 bags of 80 lb. See…
How Much Concrete Do I Need for a Slab? A 10×10 Example
Read article: How Much Concrete Do I Need for a Slab? A 10×10 ExampleWork out how much concrete a slab needs, with a full 10 x 10 foot example in cubic feet, cubic yards and bags, plus…
What Is Break-Even ROAS? Formula, Examples and How to Use It
Read article: What Is Break-Even ROAS? Formula, Examples and How to Use ItBreak-even ROAS is the return on ad spend at which an order pays for itself. Learn the formula, see worked examples and find your…
Markup vs Margin: What Is the Difference? Formulas and Examples
Read article: Markup vs Margin: What Is the Difference? Formulas and ExamplesMarkup and margin both describe profit, but they divide by different numbers. Here are the formulas, worked examples and a conversion table.
Dog Years to Human Years: Why the 7x Rule Is a Myth
Read article: Dog Years to Human Years: Why the 7x Rule Is a MythWhy multiplying a dog’s age by 7 is wrong. See the size-based chart, the UC San Diego formula and a free dog age calculator.
How to Calculate Roof Pitch: Formula, Chart and Examples
Read article: How to Calculate Roof Pitch: Formula, Chart and ExamplesLearn how to calculate roof pitch from rise and run, with the formula, a pitch-to-angle chart and worked examples.
How eBay Fees Work in 2026: What eBay Takes From Every Sale
Read article: How eBay Fees Work in 2026: What eBay Takes From Every SaleHow eBay seller fees work in 2026: the final value fee, the per-order fee and worked examples. Learn what you keep from a sale.