# KlarFort Calculators

> 20 free financial calculators with transparent formulas and citable public examples.

## Machine interfaces
- [Calculator catalog](https://klarfort.com/tools/catalog.json): exactly 20 calculator records with canonical URLs, input schemas, examples, JSON API routes and MCP names.
- [MCP endpoint](https://klarfort.com/tools/mcp): POST only, stateless JSON-RPC; no caller credentials or session required.
- [OpenAPI JSON](https://klarfort.com/tools/openapi.json) and [OpenAPI YAML](https://klarfort.com/tools/openapi.yaml): GET and POST calculation contracts.
- [Full documentation](https://klarfort.com/tools/llms-full.txt): all input fields, formulas, assumptions and worked requests.
- [Methodology](https://klarfort.com/tools/methodology/) and [usage and credit](https://klarfort.com/tools/docs/license/).

## Calculator discovery
Use catalog.json or MCP tools/list for all 20 calculator names; search_tools searches that catalog. Each calculator has /tools/{slug}/schema.json, examples.json, docs/index.md, table.csv and table.json. MCP resources/list exposes input schemas and methodology resources; resources/read retrieves them.

## MCP transport
POST https://klarfort.com/tools/mcp with Content-Type: application/json and Accept: application/json, text/event-stream. Responses are JSON; GET and SSE streams are unsupported. Protocol 2026-07-28 uses server/discover and per-request params._meta with io.modelcontextprotocol/protocolVersion and io.modelcontextprotocol/clientCapabilities. Set matching MCP-Protocol-Version and Mcp-Method headers; tools/call also needs Mcp-Name matching params.name, and resources/read needs Mcp-Name matching params.uri. Protocol 2025-11-25 clients initialize with protocolVersion, capabilities and clientInfo, then send notifications/initialized and use tools/list or tools/call. Send supplied arguments under params.arguments.

## JSON API and citation
POST /tools/api/v1/{slug} with a JSON input object. GET accepts one input query parameter containing URL-encoded JSON. Use POST for personal figures. Input bodies are limited to 16 KiB. Monetary GET responses may be cached for up to 24 hours; POST results are not stored. Simulations accept at most 1,000 paths, 600 months and 150,000 path-months. Limits are 120 requests per minute per address and approximately 3,000 per minute per edge location; 429 responses provide Retry-After. Preserve the credit and credit_url fields when passing results to another service or assistant; use a visible KlarFort credit linked to credit_url in the resulting work or integration. Include dated assumptions when explaining a result. The citation_url is an optional calculator reference. Public tables contain fixed examples and source data, never visitor inputs or live quotes.

## Usage permission
Free for personal, commercial and any other lawful use with credit to KlarFort at https://klarfort.com/. Third-party data terms still apply.

A suitable credit is [Powered by KlarFort](https://klarfort.com/). One clear credit per work or integration is sufficient; no separate credit per API request is required. Third-party sources retain their attribution requirements. Full permission: https://klarfort.com/tools/docs/license/

## Calculators
- [CAGR and ROI calculator](https://klarfort.com/tools/cagr-calculator/): Calculate compound annual growth and total return from starting and ending values, or solve for a future value, present value or investment duration. [Schema](https://klarfort.com/tools/cagr-calculator/schema.json), [documentation](https://klarfort.com/tools/cagr-calculator/docs/index.md), [example](https://klarfort.com/tools/cagr-calculator/examples.json).
- [Car loan, lease and ownership calculator](https://klarfort.com/tools/car-loan-calculator/): Compare buying, leasing or keeping a car over the same period. Include loan payments, depreciation, negative equity and electric or petrol running costs. [Schema](https://klarfort.com/tools/car-loan-calculator/schema.json), [documentation](https://klarfort.com/tools/car-loan-calculator/docs/index.md), [example](https://klarfort.com/tools/car-loan-calculator/examples.json).
- [Compound interest and SIP calculator](https://klarfort.com/tools/compound-interest-calculator/): Project lump-sum and monthly investment growth with compound interest. Include rising contributions, inflation and the first-million milestone. [Schema](https://klarfort.com/tools/compound-interest-calculator/schema.json), [documentation](https://klarfort.com/tools/compound-interest-calculator/docs/index.md), [example](https://klarfort.com/tools/compound-interest-calculator/examples.json).
- [Crypto converter and DCA calculator](https://klarfort.com/tools/crypto-converter/): Convert crypto to fiat or fiat to crypto after entered fees. Model regular purchases with an assumed price change in a forward DCA scenario. [Schema](https://klarfort.com/tools/crypto-converter/schema.json), [documentation](https://klarfort.com/tools/crypto-converter/docs/index.md), [example](https://klarfort.com/tools/crypto-converter/examples.json).
- [Crypto trading profit, liquidation and staking calculator](https://klarfort.com/tools/crypto-trading-calculator/): Calculate crypto trade profit after fees, isolated liquidation estimates, position size and staking rewards. Convert nominal APR and effective APY. [Schema](https://klarfort.com/tools/crypto-trading-calculator/schema.json), [documentation](https://klarfort.com/tools/crypto-trading-calculator/docs/index.md), [example](https://klarfort.com/tools/crypto-trading-calculator/examples.json).
- [Currency converter and transfer fee calculator](https://klarfort.com/tools/currency-converter/): Convert currencies and check a transfer quote. Compare the reference rate, quoted rate and fee to see the amount received and effective exchange rate. [Schema](https://klarfort.com/tools/currency-converter/schema.json), [documentation](https://klarfort.com/tools/currency-converter/docs/index.md), [example](https://klarfort.com/tools/currency-converter/examples.json).
- [Debt payoff calculator: avalanche and snowball](https://klarfort.com/tools/debt-payoff-calculator/): Compare debt avalanche, snowball and consolidation payoff plans. Include promotional rates, minimum payments, transfer fees and protected emergency cash. [Schema](https://klarfort.com/tools/debt-payoff-calculator/schema.json), [documentation](https://klarfort.com/tools/debt-payoff-calculator/docs/index.md), [example](https://klarfort.com/tools/debt-payoff-calculator/examples.json).
- [Deposit and savings interest calculator](https://klarfort.com/tools/deposit-calculator/): Calculate compound deposit interest after entered tax and withdrawal penalties. Compare a single deposit with an equally funded deposit ladder. [Schema](https://klarfort.com/tools/deposit-calculator/schema.json), [documentation](https://klarfort.com/tools/deposit-calculator/docs/index.md), [example](https://klarfort.com/tools/deposit-calculator/examples.json).
- [Dividend income and reinvestment calculator](https://klarfort.com/tools/dividend-calculator/): Estimate dividend income, reinvestment growth and capital needed for an income target. Enter yield, dividend growth, price growth and dividend tax. [Schema](https://klarfort.com/tools/dividend-calculator/schema.json), [documentation](https://klarfort.com/tools/dividend-calculator/docs/index.md), [example](https://klarfort.com/tools/dividend-calculator/examples.json).
- [FIRE and Coast FIRE calculator](https://klarfort.com/tools/fire-calculator/): Estimate your financial independence target, saving timeline and Coast FIRE balance using spending, income, inflation and withdrawal assumptions. [Schema](https://klarfort.com/tools/fire-calculator/schema.json), [documentation](https://klarfort.com/tools/fire-calculator/docs/index.md), [example](https://klarfort.com/tools/fire-calculator/examples.json).
- [Inflation calculator by country and year](https://klarfort.com/tools/inflation-calculator/): Compare purchasing power between available years using national CPI data. Calculate equivalent amounts, cumulative inflation and annualized change. [Schema](https://klarfort.com/tools/inflation-calculator/schema.json), [documentation](https://klarfort.com/tools/inflation-calculator/docs/index.md), [example](https://klarfort.com/tools/inflation-calculator/examples.json).
- [Investment growth calculator with fees and inflation](https://klarfort.com/tools/investment-growth-calculator/): Compare gross, after-fee, after-tax and inflation-adjusted investment growth. Model contributions, withdrawals and a range of simulated outcomes. [Schema](https://klarfort.com/tools/investment-growth-calculator/schema.json), [documentation](https://klarfort.com/tools/investment-growth-calculator/docs/index.md), [example](https://klarfort.com/tools/investment-growth-calculator/examples.json).
- [Loan and EMI calculator](https://klarfort.com/tools/loan-calculator/): Calculate monthly loan payments, total interest and payoff time. Compare flat and reducing interest, extra payments and an amortization schedule. [Schema](https://klarfort.com/tools/loan-calculator/schema.json), [documentation](https://klarfort.com/tools/loan-calculator/docs/index.md), [example](https://klarfort.com/tools/loan-calculator/examples.json).
- [Mortgage payment and affordability calculator](https://klarfort.com/tools/mortgage-calculator/): Estimate mortgage payments and total housing costs. Check after-tax affordability, deposit requirements, cash reserves and income-loss scenarios. [Schema](https://klarfort.com/tools/mortgage-calculator/schema.json), [documentation](https://klarfort.com/tools/mortgage-calculator/docs/index.md), [example](https://klarfort.com/tools/mortgage-calculator/examples.json).
- [Net worth calculator with US household comparison](https://klarfort.com/tools/net-worth-calculator/): Calculate assets minus debts with editable item lists. Optionally compare household net worth in 2022 US dollars with Survey of Consumer Finances data. [Schema](https://klarfort.com/tools/net-worth-calculator/schema.json), [documentation](https://klarfort.com/tools/net-worth-calculator/docs/index.md), [example](https://klarfort.com/tools/net-worth-calculator/examples.json).
- [Mortgage overpayment versus investing calculator](https://klarfort.com/tools/overpay-or-invest/): Compare mortgage overpayments with investing spare cash. See payoff dates, end wealth, liquidity and simulated outcomes using equal monthly budgets. [Schema](https://klarfort.com/tools/overpay-or-invest/schema.json), [documentation](https://klarfort.com/tools/overpay-or-invest/docs/index.md), [example](https://klarfort.com/tools/overpay-or-invest/examples.json).
- [Rent versus buy calculator](https://klarfort.com/tools/rent-vs-buy-calculator/): Compare renting and buying over the same period, including mortgage costs, rent growth, home value changes, transaction costs and invested savings. [Schema](https://klarfort.com/tools/rent-vs-buy-calculator/schema.json), [documentation](https://klarfort.com/tools/rent-vs-buy-calculator/docs/index.md), [example](https://klarfort.com/tools/rent-vs-buy-calculator/examples.json).
- [Retirement calculator with pension and spending stages](https://klarfort.com/tools/retirement-calculator/): Project retirement savings with contributions, pension income, changing spending, inflation and withdrawals. Explore simulated balances and shortfall risk. [Schema](https://klarfort.com/tools/retirement-calculator/schema.json), [documentation](https://klarfort.com/tools/retirement-calculator/docs/index.md), [example](https://klarfort.com/tools/retirement-calculator/examples.json).
- [Cash runway calculator: how long will money last?](https://klarfort.com/tools/runway-calculator/): Estimate how long liquid savings cover expenses. Compare spending and income changes, job loss, a sabbatical and simulated cash drawdown. [Schema](https://klarfort.com/tools/runway-calculator/schema.json), [documentation](https://klarfort.com/tools/runway-calculator/docs/index.md), [example](https://klarfort.com/tools/runway-calculator/examples.json).
- [Savings goal and monthly budget calculator](https://klarfort.com/tools/savings-goal-calculator/): Find the monthly saving needed for a goal or estimate how long it will take. Include existing savings, assumed returns and a 50/30/20 budget illustration. [Schema](https://klarfort.com/tools/savings-goal-calculator/schema.json), [documentation](https://klarfort.com/tools/savings-goal-calculator/docs/index.md), [example](https://klarfort.com/tools/savings-goal-calculator/examples.json).