Who We Are
Thrive Calculator was originally developed by Agus Purwantoro, a software developer who got tired of calculator sites that were either too complex or cluttered.
The idea came from repeatedly needing to check platform fees for different payment processors and finding existing tools either outdated, ad-heavy, or hard to trust.
At first, it started as a side project to build a reliable calculator for e-commerce fees and then expanded into a full collection of calculators covering math, personal finance, health metrics, and everyday tools.
What We Build
Core calculators: Basic, Advanced, and Scientific calculators with a full keypad interface, calculation history, and keyboard shortcuts.
Math calculators: Percentage change and proportion, fraction operations and conversion, statistics (mean, median, mode, standard deviation, variance, quartiles), and averages (arithmetic, weighted, geometric, harmonic).
Financial calculators: Loan amortization, mortgage payments, tax estimates, VAT by country, salary breakdowns, budget planning (50/30/20, expense tracking, savings goals, emergency funds), and discount comparisons.
Health calculators: BMI with metric, imperial, and child/teen modes using CDC BMI-for-age percentile data. Calorie calculators with three BMR formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and six activity levels. Body fat via the U.S. Navy Method or BMI method. Protein intake based on weight and activity.
Everyday tools: Age, date difference, fuel cost, time conversion, split bill, tip, and freelance rate calculators.
Fee calculators: PayPal (country-specific rates), Stripe, Wise (currency pairs with volume discounts), Square, Venmo, Cash App, Escrow.com, Upwork, Fiverr, and Flippa. Rates are based on official pricing pages and periodically updated.
How We Keep Results Accurate
mathjs engine: All calculations handled by mathjs and no plain JavaScript, mathjs handles floating-point precision correctly without rounding errors.
Sourced data: Fee calculator rates are based on official sources: PayPal's country pricing pages, Wise's fee structure, Stripe's regional documentation. When platforms update rates, we also update them.
Multi-formula support: Health calculators that offer multiple methods (BMR formulas, body fat methods) let you compare results side by side.
Real-world testing: Every calculator is passed multiple tests before release. Loan amortization schedules are verified against standard financial formulas. BMI results are cross-checked against CDC and WHO reference tables.
Peer review: Calculators with financial or health data are carefully checked against official sources before they are released.
Our Approach to Privacy
- No account required. We don't need you to create account on this website.
- Calculation history is stored in your browser's localStorage. It never leaves your device.
- We do not store logs, sell your data, share it with marketers, or build advertising profiles.
Please read our full Privacy Policy and Terms of Service.
Transparency
- We are not affiliated with PayPal, Stripe, Wise, or any other platform listed on this website. Our fee calculators are independent tools for estimation.
- Financial and health results are estimates based on the inputs you provide. Always consult a qualified professional before making major decisions.
- We participate in the Amazon Associates program. Product recommendations are based on research, not commission rates.
Technology
The site is built with Next.js 16 (App Router), React 19, and TypeScript. We use mathjs for calculations, Tailwind CSS for styling, and shadcn/ui for accessible components.
Get in Touch
Found a bug? Think our calculator is missing a feature? Want to suggest a new tool? Visit our Contact Us page.