About Finzs

Our Mission

Finzs was born from a simple belief: everyone deserves access to clear, accurate, and private financial planning tools — without paywalls, account registrations, or data harvesting.

Whether you’re a freelancer navigating the labyrinth of self-employment taxes, a young professional planning your first retirement account, or a family budgeting for a mortgage, the financial world is complex enough without opaque calculators adding to the confusion. We build tools that strip away the noise and show you the numbers that matter.

Every calculator on Finzs runs entirely in your browser. Your salary, your savings, your debt — none of it leaves your device. We don’t use trackers, we don’t sell data, and we never will.

What Makes Finzs Different

Privacy-first architecture. All calculations happen client-side in your browser using JavaScript. No data is transmitted to any server. You can verify this by opening your browser’s developer tools — you’ll see zero network requests during calculations.

Professional-grade accuracy. Our tax calculator uses 2025 IRS progressive tax brackets across all 50 states with their unique tax structures. Our currency converter supports 160+ global currencies with live exchange rates via the Frankfurter API. Every formula is documented and transparent.

Multilingual by design. Finzs is available in English, French, German, Japanese, and Arabic — with full right-to-left support. Language switchers are always one click away, and all tool labels, results, and charts adapt instantly.

Dark mode first. Built from the ground up for dark-mode readability, with a carefully tuned light mode alternative. The interface uses the Fraunces display typeface paired with DM Sans for body text and JetBrains Mono for numeric data — a typographic system designed for clarity at a glance.

Open source ethos. While not currently open source, our calculations and methodologies are fully documented. We believe financial literacy requires transparency, and we’re committed to explaining not just the results, but how we arrive at them.

How to Use Finzs

Getting started with Finzs is straightforward. Here’s a quick tour of each calculator and how to get the most out of it:

Freelancer Tax Calculator

Enter your annual gross income, select your filing status (Single, Married Filing Jointly, or Head of Household), choose your state of residence, and optionally input business expenses, health insurance premiums, and retirement contributions.

The calculator applies the standard deduction for your filing status (2025 values), then computes federal income tax using the IRS progressive bracket system, state income tax using your state’s specific brackets (or zero for no-tax states like Texas and Florida), and self-employment tax at 15.3% on 92.35% of your net business income.

The result panel shows your after-tax income annually and monthly, with a detailed breakdown of each tax component and your effective tax rate. Use this to plan quarterly estimated tax payments or evaluate whether forming an S-Corp might benefit you.

Retirement Savings Calculator

Set your current age and target retirement age using the sliders. Enter your current savings balance, monthly contribution amount, and expected annual return rate. If you have an employer match, adjust the match percentage and cap sliders.

The calculator computes your projected retirement balance using compound interest applied monthly. The interactive chart visualizes your portfolio growth trajectory from now through retirement, making it easy to see how even small increases in monthly contributions dramatically affect your final nest egg.

Pro tip: Try increasing your monthly contribution by just 1% of your income and watch the compound effect over 30+ years — it’s often surprisingly large.

Compound Interest Calculator

Input your initial investment, monthly addition, expected annual interest rate, and investment period in years. The stacked chart shows how much of your final balance comes from your contributions versus pure interest earnings.

This is the most powerful financial concept to understand: time is the multiplier. An extra 10 years of compounding can more than double your eventual balance, even without increasing your monthly contribution.

Mortgage Calculator

Enter the home price, adjust the down payment percentage slider, set the interest rate and loan term. The calculator shows your monthly payment broken into principal and interest, total payment over the loan lifetime, and total interest cost.

The bar chart visualizes the amortization profile — how much of each payment goes toward principal versus interest over the life of the loan. This makes it easy to understand why a 15-year mortgage saves so much compared to a 30-year term.

Currency Converter

Select your source and target currencies from the dropdown menus, enter the amount, and get an instant conversion. Use the swap button between the two currency selectors to quickly reverse the conversion direction.

Exchange rates are sourced live from the Frankfurter API (84 central banks, 201 currencies) and cached in your browser for 1 hour. While rates are current, this tool is designed for estimation and planning — for real-time trading or large transfers, always check your bank or broker’s current rate.

ROI Calculator

Enter your initial investment amount, expected annual revenue or savings generated by the investment, annual operating costs, and the holding period in years. The calculator computes your total net profit, ROI percentage, annualized ROI, and payback period.

Use this to evaluate business investments, equipment purchases, marketing campaigns, or any scenario where you want to understand the return relative to the upfront cost. The payback period tells you how quickly you’ll recoup your initial investment.

Budget Planner

Start with your monthly after-tax income. The 50/30/20 rule allocates 50% to needs (housing, utilities, groceries), 30% to wants (entertainment, dining, travel), and 20% to savings and debt repayment. Adjust each slider to customize the percentages to your situation.

The color-coded progress bars give you an at-a-glance view of your allocation. The remaining balance indicator turns red if you’ve allocated more than 100% — a helpful budgeting reality check.

Loan Payoff Calculator

Enter your current loan balance, interest rate, and minimum monthly payment. Then add an extra monthly payment amount to see how much faster you can become debt-free. The line chart overlays two payoff curves — one with minimum payments only, one with extra payments — so you can visually compare the timelines.

The calculator also shows total interest paid in both scenarios, making the savings from accelerated payments immediately clear. Even a modest extra payment of $50-100 per month can shave years off a loan and save thousands in interest.

Technology Stack

Finzs is built with Astro 6 for static site generation, React 19 for interactive calculators, Tailwind CSS v4 for styling, and shadcn/ui components built on Radix UI primitives. Charts are rendered with Recharts. The entire site generates as static HTML with client-side JavaScript hydration only where needed.

Our choice of static generation means the site loads nearly instantly and can be hosted on any CDN or static file server. No databases, no backend servers, no API keys required for visitors.