About PowerBankMath
PowerBankMath is the battery arithmetic: what a 20,000 mAh bank actually charges, how long the recharge takes, and whether it can run the laptop.
PowerBankMath exists because power banks are labeled in mAh nobody can use (3.7 V cells vs 5 V output) and charged at speeds the marketing ignores. The conversions are simple; seeing them is the difference between a bank that works and a paperweight.
Every calculator on PowerBankMath shows its formula and its assumptions on the page, so you can check the math, reproduce it in a spreadsheet, or argue with it. Inputs are processed entirely in your browser — nothing is sent to a server, and there are no accounts.
PowerBankMath is an independent, ad-supported project. We are not affiliated with any lender, brand, agency, or the sources we cite (manufacturer specifications and published standards). If a number looks wrong, the contact page reaches a human who fixes it.
What makes PowerBankMath different
- Your numbers never leave your browser. Every calculator on PowerBankMath runs entirely on your device. We never see, store, or transmit the figures you enter — there are no accounts and no server-side processing of your inputs.
- Published methodology. Each calculator page explains the exact formula it uses and the assumptions behind it, so you can check our work or reproduce it in a spreadsheet.
- Free, forever, without a paywall. PowerBankMath is supported by advertising. There is no premium tier, no email gate, and no upsell.
Independence
PowerBankMath is an independent educational project. We are not affiliated with, endorsed by, or acting on behalf of any government agency, lender, insurer, or the organizations whose formulas and public data we reference (such as manufacturer specifications and published standards). All trademarks and referenced standards belong to their respective owners.
Questions, corrections, or suggestions are genuinely welcome — get in touch.