Mortgage Calculator
Calculate monthly mortgage payment, total interest, and amortization schedule.
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Calculator Tools
Free, browser-based calculators for everyday personal-finance, math, sustainability, and engineering tasks: mortgage payment math, percentage problems, currency conversion, carbon footprint estimation, and Unix timestamp conversion. Instant results, no signup, no install.
Percentage Calculator
Compute percentages, percent change, percent of total, and inverse percentage problems.
Currency Converter
Convert between major currencies with live or recent exchange rates.
Carbon Footprint Calculator
Estimate household or activity carbon emissions in metric tons of CO2 equivalent.
Timestamp Converter
Convert between Unix epoch timestamps and human-readable dates across time zones.
When a quick calculator beats a spreadsheet
Most of these calculations can be done in Excel, Google Sheets, or a programming language — but the activation energy of opening a spreadsheet for a single computation is higher than typing two numbers into a focused web tool. The calculators on this hub are scoped to the “I need an answer in 5 seconds” case.
Personal finance: mortgage and percentage
The Mortgage Calculator computes the monthly principal-and-interest payment using the standard amortization formula. Inputs: loan amount, interest rate, term in years. The output is exactly what a bank's loan estimate shows under “principal and interest” — useful for comparing offers from different lenders without their sales pitch.
The Percentage Calculator handles the four common percentage problems: what is X% of Y, X is what percent of Y, percent change from X to Y, and inverse (X is Y% of what). Together they cover the math behind tip calculations, discount comparisons, growth rates, and reverse-engineering original prices from sale prices.
Currency: travel and international workflows
The Currency Converter uses a public rate feed for the major currencies. Use it for travel budgeting, freelance invoicing across currencies, and rough estimates of foreign pricing. For trading or hedging decisions, use a real-time forex broker — public rate feeds lag the market by minutes to hours.
Sustainability: carbon footprint awareness
The Carbon Footprint Calculator gives an order-of-magnitude estimate of CO2 emissions from household or activity inputs (electricity, fuel, miles driven, food). Useful for personal awareness and pre-launch sustainability claims, not for regulated carbon reporting — that requires GHG Protocol or ISO 14064 methodology with audit trails.
Engineering: Unix timestamps
The Timestamp Converter is the most-used calculator on this hub for developers. Almost every log file, database column, API response, and analytics event uses Unix epoch timestamps. Converting them to a human-readable date for debugging — or back from a date for setting an API parameter — is something you do dozens of times a week as soon as you work with backend systems.
What these calculators do not do
They do not replace professional judgment for high-stakes decisions:
- Mortgage — get a full loan estimate from a licensed lender that includes taxes, insurance, PMI, points, and closing costs.
- Currency — for any transaction over a few hundred dollars, check the live spread from your bank or broker.
- Carbon — for regulatory or B-corp reporting, use certified methodologies with audit trails.
- Timestamps — for production code, use a proper date library (date-fns, Luxon) rather than ad-hoc conversion.
Privacy
Every calculator runs in your browser. Inputs are not sent to a server, not logged, and not stored. Closing the tab discards everything.
Related hubs
- Developer Tools Hub — for the broader set of programming utilities.
- Text & Writing Tools — for content production calculators (reading time, word counts).