Calculators

Free, fast calculators that run entirely in your browser, with no sign-up and nothing sent to a server. Pick a group below, or go straight to a tool. Every calculator comes with a plain-English explanation of its formula, a worked example and a list of its limits.

Browse by group

Seller and Business Calculators

Fees, pricing and advertising break-even for online sellers.

Home and Energy Calculators

Roof, concrete and solar estimates for homeowners and DIY builders.

Pets and Hobby Calculators

Dog age and 3D printing cost for pet owners and makers.

What each calculator does

eBay Fee Calculatorfinal value fee, per-order fee, payout and profit from editable rates.Etsy Fee Calculatorlisting, transaction and processing fees, optional Offsite Ads, payout and profit.Break-Even ROAS Calculatorbreak-even ROAS, break-even CPA and target ROAS from your prices and costs.Markup vs Margin Calculatorconvert between markup and margin and find price and profit.Roof Pitch Calculatorpitch, angle, percent slope and rafter length from rise and run.Concrete Slab Calculatorcubic yards, cubic feet and bag counts for a slab.Solar Panel Cost Calculatorpanels needed, installation cost, net cost and yearly output.Solar Payback Calculatoryearly savings, payback period and 25-year net savings.Dog Age Calculatordog years to human years by size, plus the epigenetic formula.3D Printing Cost Calculatorthe true cost per part and a suggested price.

How to pick a calculator

Choose the group that matches your question. Sellers can start with fees and pricing, homeowners with roof, concrete and solar estimates, and pet owners and makers with dog age and 3D printing cost. Each group page explains who its tools are for and gives tips for getting accurate results.

Before you use the results

Results are estimates for information only. Rates, fees and prices that appear as defaults are placeholders, so replace them with your own current numbers. Read the Disclaimer for the limits of the tools, or visit the FAQ page if you have a question. To report a mistake, use the Contact form.