Practical tools for online sellers and marketers.
Sponge helps ecommerce teams, creators, and marketers calculate, write, and improve the small decisions that shape online growth.
Profit Margin Calculator
Calculate profit, cost, and margin for ecommerce, Shopify, Amazon, Etsy, or independent store products.
15 Guides
Helpful support content
5 Tools
Calculators and generators
6 Pages
Helpful reference pages
Editorial Growth
Guides that feel like a trusted publication
Practical guides that explain ecommerce, SEO, pricing, and content workflows around the tools.
Profit margin vs markup: how to tell the difference
Learn the difference between margin and markup before you set product prices.
How to calculate profit margin for ecommerce products
A simple walkthrough for calculating profit margin before you change product prices.
ROI examples for ads: a simple way to judge campaigns
See how ROI works with paid ads, traffic tests, and small campaign budgets.
Useful Tools
Interactive pages that attract links and repeat visits
Calculators and generators help you move from rough guesses to clearer business and content decisions.