EveryCalc

npx add-mcp 'https://everycalc.xyz/mcp'

EveryCalc

Free finance, military, school and everyday calculators, exposed as a REST API and an MCP server so AI assistants can do the math for you.

Live site: https://everycalc.xyz API docs (OpenAPI): https://everycalc.xyz/api/v1/openapi.json MCP endpoint: POST https://everycalc.xyz/mcp (Streamable HTTP, no auth)

What it is

EveryCalc is a collection of interactive calculators for money, military life, school, and everyday questions. This repo hosts the server code that powers two machine-friendly interfaces on top of those calculators:

1. REST API at everycalc.xyz/api/v1/*, plain GET endpoints, JSON in and out.
2. MCP server at POST everycalc.xyz/mcp, 69 calculator tools for Model Context Protocol clients (Claude, Cursor, and friends).

No API key. No signup. No local install for the hosted version.

Every tool result includes a calculator_url deep link to the matching interactive calculator on everycalc.xyz, so users can explore the numbers visually after the assistant does the math.

The 69 tools

Finance (28)

Tool	What it computes
calculate_401k	Projected 401k balance with employee contributions capped at 24500 per year, plus an employer match, compounded annually
calculate_affordability	Maximum home price affordable from household income using the 28/36 rule
calculate_arm_vs_fixed	Worst case adjustable rate mortgage simulation with rate caps, compared with a fixed rate loan on total interest, payments, and the breakeven year
calculate_auto_loan	Monthly payment, amount financed, total interest, and total cost of a car for an auto loan after down payment and trade-in value are subtracted from the vehicle price
calculate_biweekly_mortgage	Interest and time saved by paying half the monthly mortgage payment every two weeks instead of monthly
calculate_capital_gains_tax	Federal tax on ordinary income plus short term gains at ordinary rates, with long term gains stacked at the 0, 15, and 20 percent thresholds for the filing status
calculate_car_affordability	Monthly loan payment plus running costs (insurance, fuel, and maintenance, given as annual amounts), total interest, and the five year cost of a car
calculate_compound_interest	Future value of an investment with monthly contributions and monthly compounding
calculate_credit_card_payoff	Months and interest to clear a credit card balance with a fixed monthly payment, compared with adding an extra monthly payment
calculate_debt_payoff	Simulates paying off a list of debts month by month with minimum payments plus an extra monthly payment, comparing the avalanche method (highest APR first) with the snowball method (smallest balance first), and reports months to payoff
calculate_emergency_fund	Target emergency fund for a chosen number of months of essential expenses, the remaining gap, percent funded, and months to fill it at a monthly savings rate
calculate_income_tax_estimator	Federal income tax after pretax deductions and the standard deduction for the filing status, with AGI, taxable income, marginal rate, and effective rate
calculate_inflation	What an amount in today's dollars will buy after a number of years at a given annual inflation rate, what today's basket will cost then, the cumulative price increase percent, and the purchasing power lost
calculate_lease_vs_buy	Lease outlay over the lease term versus buy outlay net of equity in the car at the same point, with the winning option and the net cost difference
calculate_loan	Monthly payment, total interest, and optional amortization schedule for an amortizing loan
calculate_mortgage	Monthly mortgage payment breakdown: principal and interest via the amortization formula, plus property tax, homeowner insurance, PMI, and HOA
calculate_net_worth	Net worth, total assets, and total liabilities from comma separated asset and liability values, with optional matching names for the largest asset and liability
calculate_paycheck	Per paycheck net pay after federal income tax, FICA (Social Security capped at 184500 of wages, Medicare, and the additional Medicare tax), a flat state tax rate, and pretax deductions
calculate_property_tax_estimator	Annual and monthly property tax from the home value minus any exemption, at the given tax rate, with assessed value and effective rate
calculate_raise_vs_inflation	Whether a raise beats inflation: nominal new salary, inflation adjusted real salary, the real percent change, and a real raise, real pay cut, or flat verdict
calculate_refinance	Refinance break-even month and lifetime savings of refinancing a loan
calculate_rent_vs_buy	Compares the net cost of buying a home (down payment, mortgage payments, tax, insurance, and maintenance, minus principal repaid and appreciation gain) with the total rent paid over the years you plan to stay
calculate_retirement_savings_planner	Projected retirement balance from current savings plus monthly contributions with monthly compounding, total contributions, growth, and a 4 percent rule withdrawal figure
calculate_roth_conversion	Value of converting to a Roth now, with the tax paid out of the converted amount, versus leaving the money in a traditional account taxed at the retirement rate, after growth
calculate_roth_vs_traditional	Compares a Roth and a traditional retirement account at the same pre-tax annual contribution: the Roth invests what is left after tax today and is tax free at withdrawal
calculate_salary	Convert between hourly, daily, weekly, biweekly, monthly, and annual pay
calculate_sba_loan	Monthly payment for an SBA loan with the guarantee fee percent financed into the loan, plus the amount financed, total interest, and total cost
calculate_social_security_estimator	Primary insurance amount from the bend point formula (1286 and 7749) applied to average indexed monthly earnings, with monthly benefits at ages 62, 67, and 70

Military (11)

Tool	What it computes
calculate_aft	Scores all five AFT events (deadlift, hand-release push-ups, sprint-drag-carry, plank, 2-mile run) from 0 to 100 each using the 17-21 anchor tables, for a 500-point total
calculate_bah	Monthly Basic Allowance for Housing from the 2026 RC/Transient baseline rate table by pay grade, with or without dependents, plus the annualized amount
calculate_brs_vs_high3	Pension-only comparison of the legacy High-3 system (2.5 percent per year of service) against the Blended Retirement System (2.0 percent per year) on the same high-3 average basic pay: monthly, annual, and 30-year lifetime differences
calculate_gi_bill	Months of the 36-month Post-9/11 GI Bill entitlement remaining, tuition coverage percent, maximum annual books stipend, and Monthly Housing Allowance treatment for the given benefit tier and enrollment level
calculate_les_decoder	Net pay from a Leave and Earnings Statement: sums the entitlement lines (base pay, BAH, BAS, other) and deduction lines (federal tax, FICA, state tax, SGLI, TSP, other), and returns net pay plus deductions as a percent of entitlements
calculate_military_pay	Monthly basic pay from the 2026 pay table for a pay grade and years of service, plus the annualized amount
calculate_military_retirement_pension	Monthly retired pay estimate: years of service times the system multiplier (2.0 percent per year for BRS, 2.5 percent per year for High-3) times the high-3 average monthly basic pay, before taxes, plus annual and 20-year lifetime amounts
calculate_pcs_move	Estimated PCS move money: Dislocation Allowance (DLA) plus Temporary Lodging Expense (TLE, days capped at 21) plus the gross Personally Procured Move (PPM) reimbursement, with the PPM profit after moving costs
calculate_sgli_vs_private_insurance	Cost comparison of SGLI (0.06 USD per 1,000 USD of coverage per month plus a 1 USD monthly fee) against a private term premium over the given number of years: monthly and total SGLI cost, total private cost, and which is cheaper
calculate_tsp	Projected TSP balance with annual employee contributions (capped at the 24,500 USD elective deferral limit used by the page) plus, when matching is on
calculate_va_disability	Monthly VA disability compensation from the 2026 rates (2.8 percent COLA, effective Dec 1, 2025) for a combined rating from 10 to 100 percent and a dependent status, plus the annualized amount

School (23)

Tool	What it computes
calculate_act_score	Composite, STEM, and ELA scores from the four ACT section scores, each clamped to 1 to 36 exactly as the page does
calculate_ap_exam_score	Predicted AP score from 1 to 5 using the page bands on the weighted composite percent: multiple choice and free response contributions are weighted by the exam split, then banded at 70, 55, 40, and 25 percent
calculate_college_acceptance	Rough acceptance chance: a selectivity tier base rate (92, 80, 50, 20, or 5 percent) adjusted by GPA and test score bands, clamped to 1 to 99 percent and labeled Safety, Target, Reach, or High reach
calculate_college_major_roi	Payback years, lifetime earnings minus degree cost, and salary to cost ratio for a major, using the page table of approximate median early career salaries by major
calculate_college_roi	Earnings premium of a degree salary over a no degree baseline salary, both growing at the same annual raise rate, plus the net gain after degree cost, the break-even year, and the return multiple on cost
calculate_dorm_vs_apartment	Compares the annual dorm cost with an apartment: monthly rent over the number of months, plus annual utilities, extra food cost, and commuting cost
calculate_fafsa_sai_estimator	Simplified Student Aid Index estimate using the page formula: parent income at 22 percent plus parent assets at 12 percent, student income above the 11770 income protection allowance at 50 percent plus student assets at 20 percent
calculate_final_exam	Score needed on the final exam to reach a desired course grade, with the best and worst possible course grades
calculate_gpa	Credit weighted GPA on the 4.0 scale using the page grade points: A+ and A 4.0, A- 3.7, B+ 3.3, B 3.0, B- 2.7, C+ 2.3, C 2.0, C- 1.7, D+ 1.3, D 1.0, F 0.0
calculate_gpa_planner	Term GPA required over the planned credits to reach a target cumulative GPA, the maximum reachable cumulative GPA with straight As, and the grade mix the required GPA implies, using the page thresholds
calculate_graduate_school_roi	Annual salary premium after a graduate degree, break-even years on the total cost, and lifetime net over the career years, using the page formulas
calculate_gre_score_estimator	Estimated GRE verbal and quant scores on the 130 to 170 scale: 130 plus the fraction of questions correct times 40, per section, plus the total
calculate_high_school_course_planner	Credits still needed per subject against the page requirement table for the selected state (Texas, California, New York, Florida, or Illinois)
calculate_lsat_score_estimator	Estimated LSAT scaled score on the 120 to 180 scale: 120 plus the overall fraction correct across the three sections times 60, with accuracy and the page score band
calculate_mcat_score_estimator	Estimated MCAT section scores on the 118 to 132 scale: 118 plus the fraction correct times 14, per section, plus the total on the 472 to 528 scale
calculate_premed_course_planner	Progress across the 13 premed prerequisites on the page, in page order: General Chemistry I and II, Organic Chemistry I and II, Biology I and II, Physics I and II, Biochemistry, Psychology, Sociology, Statistics or Calculus
calculate_psat_score	Estimated PSAT section scores: 160 plus the fraction correct times 600, using the page fixed totals of 48 questions per section, plus the total and the page percentile band
calculate_sat_score	Estimated SAT section scores: 200 plus the fraction correct times 600, using the page fixed totals of 54 reading and writing questions and 44 math questions, plus the total and the page competitiveness band
calculate_scholarship_roi_tracker	Expected value of a scholarship application (award times win probability, clamped to 0 to 100 percent) and its expected value per hour of work, with the page verdict comparing that rate with an hourly wage
calculate_student_budget	Monthly budget from job, parent, and aid income against rent, food, books, transport, and fun spending
calculate_student_loan_payoff	Months to pay off a student loan and the total interest, computed month by month exactly as the page does
calculate_textbook_cost	Net cost of buying new, buying used, renting, and digital for a textbook
calculate_transfer_credit_planner	Credits remaining, terms remaining at the credits taken per term, years remaining at the terms per year, and credits per year

Everyday (7)

Tool	What it computes
calculate_age	Exact age from a birth date to a target date, broken into years, months, and days, plus total days lived, total hours lived, the weekday of birth, and days until the next birthday
calculate_bmi_tdee	Body mass index and category, Mifflin-St Jeor basal metabolic rate, total daily energy expenditure, and cut and bulk calorie targets
calculate_date_duration	Inclusive number of days between two dates, plus business days after optionally excluding weekends and 2026 US federal holidays, calendar weeks, weekend days, and holidays in the range
calculate_percentage	Percentage calculations in three modes: percent_of (x percent of y), what_percent (x is what percent of y), percent_change (change from old to new)
calculate_tip	Tip amount, bill total, and per-person split
calculate_unit_converter	Converts a value between units in one category: length, weight, temperature, volume, or speed
calculate_word_counter	Counts words, characters, characters excluding whitespace, sentences, and paragraphs in a block of text, plus estimated reading time at 200 words per minute and speaking time at 130 words per minute

Use the hosted MCP server

Add this to your MCP client config:

{
  "mcpServers": {
    "everycalc": {
      "url": "https://everycalc.xyz/mcp"
    }
  }
}

That is the whole setup. The server is remote (Streamable HTTP), so there is nothing to install. Ask your assistant a money, military, school, or everyday math question and it can call the matching tool, then follow the calculator_url in the result to open the full interactive calculator.

Use the REST API

All endpoints are GET with query parameters. Example:

GET https://everycalc.xyz/api/v1/calculate/mortgage?home_price=400000&down_payment_pct=20&annual_rate_pct=6.5&term_years=30

Response:

{
  "ok": true,
  "tool": "calculate_mortgage",
  "inputs": { "homePrice": 400000, "annualRatePct": 6.5, "termYears": 30, "...": "..." },
  "results": {
    "loan_amount": 320000,
    "down_payment_usd": 80000,
    "monthly_principal_interest": 2022.62,
    "monthly_total": 2022.62,
    "total_interest": 408142.36,
    "total_cost": 808142.36
  },
  "calculator_url": "https://everycalc.xyz/mortgage-calculator/"
}

Available endpoints (full spec in openapi.json):

• GET /api/v1/health
• GET /api/v1/openapi.json
• GET /api/v1/calculate/401k
• GET /api/v1/calculate/affordability
• GET /api/v1/calculate/arm-vs-fixed
• GET /api/v1/calculate/auto-loan
• GET /api/v1/calculate/biweekly-mortgage
• GET /api/v1/calculate/capital-gains-tax
• GET /api/v1/calculate/car-affordability
• GET /api/v1/calculate/compound-interest
• GET /api/v1/calculate/credit-card-payoff
• GET /api/v1/calculate/debt-payoff
• GET /api/v1/calculate/emergency-fund
• GET /api/v1/calculate/income-tax-estimator
• GET /api/v1/calculate/inflation
• GET /api/v1/calculate/lease-vs-buy
• GET /api/v1/calculate/loan
• GET /api/v1/calculate/mortgage
• GET /api/v1/calculate/net-worth
• GET /api/v1/calculate/paycheck
• GET /api/v1/calculate/property-tax-estimator
• GET /api/v1/calculate/raise-vs-inflation
• GET /api/v1/calculate/refinance
• GET /api/v1/calculate/rent-vs-buy
• GET /api/v1/calculate/retirement-savings-planner
• GET /api/v1/calculate/roth-conversion
• GET /api/v1/calculate/roth-vs-traditional
• GET /api/v1/calculate/salary
• GET /api/v1/calculate/sba-loan
• GET /api/v1/calculate/social-security-estimator
• GET /api/v1/calculate/aft
• GET /api/v1/calculate/bah
• GET /api/v1/calculate/brs-vs-high3
• GET /api/v1/calculate/gi-bill
• GET /api/v1/calculate/les-decoder
• GET /api/v1/calculate/military-pay
• GET /api/v1/calculate/military-retirement-pension-estimator
• GET /api/v1/calculate/pcs-move
• GET /api/v1/calculate/sgli-vs-private-insurance
• GET /api/v1/calculate/tsp
• GET /api/v1/calculate/va-disability
• GET /api/v1/calculate/act-score
• GET /api/v1/calculate/ap-exam-score
• GET /api/v1/calculate/college-acceptance
• GET /api/v1/calculate/college-major-roi
• GET /api/v1/calculate/college-roi
• GET /api/v1/calculate/dorm-vs-apartment
• GET /api/v1/calculate/fafsa-sai-estimator
• GET /api/v1/calculate/final-exam
• GET /api/v1/calculate/gpa
• GET /api/v1/calculate/gpa-planner
• GET /api/v1/calculate/graduate-school-roi
• GET /api/v1/calculate/gre-score-estimator
• GET /api/v1/calculate/high-school-course-planner
• GET /api/v1/calculate/lsat-score-estimator
• GET /api/v1/calculate/mcat-score-estimator
• GET /api/v1/calculate/premed-course-planner
• GET /api/v1/calculate/psat-score
• GET /api/v1/calculate/sat-score
• GET /api/v1/calculate/scholarship-roi-tracker
• GET /api/v1/calculate/student-budget
• GET /api/v1/calculate/student-loan-payoff
• GET /api/v1/calculate/textbook-cost
• GET /api/v1/calculate/transfer-credit-planner
• GET /api/v1/calculate/age
• GET /api/v1/calculate/bmi-tdee
• GET /api/v1/calculate/date-duration
• GET /api/v1/calculate/percentage
• GET /api/v1/calculate/tip
• GET /api/v1/calculate/unit-converter
• GET /api/v1/calculate/word-counter

Errors return {"ok": false, "error": {"code": "...", "message": "...", "field": "..."}} with an appropriate HTTP status.

Run it yourself

The server is a Cloudflare Worker. The calculation math lives in src/engine.js as pure functions (no I/O), shared by the REST handlers and the MCP handlers in src/index.js.

Prerequisites: Node 18+, wrangler.

npm install -g wrangler
wrangler login
# point [assets] directory at your static-site build, then:
wrangler deploy

The OpenAPI document is generated from the same handlers, so API docs never drift from behavior.

Tests

npm test

test/test.mjs exercises the REST endpoints against the pure math functions; test/test-mcp.mjs exercises the MCP tool handlers.

MCP registry

This repo includes server.json, the manifest for the official MCP registry, published as xyz.everycalc/every-calc.

License

MIT. See LICENSE.