BoringToolsKit

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

36 free private calculator tools for Claude. No accounts, no data leaves your session.

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Copy this into your MCP client config:

{
  "mcpServers": {
    "BoringToolsKit": {
      "url": "https://boringtoolskit.com/mcp",
      "transport": "streamable-http"
    }
  }
}

Measured tools (36)

• tip_bill_split read-only

  Split a bill across a group after tax, tip, and optional rounding. Returns each person's share, the tip, the effective tip rate, and the collected total.

  Parameters:

  • subtotal (required) — number — Pre-tax bill amount
  • tax (required) — number — Tax amount
  • tipPct (required) — number — Tip percentage (e.g. 18)
  • people (required) — number — Number of people sharing
  • tipOnTax — boolean — Whether tip is calculated on subtotal plus tax
  • roundMode — string — Rounding mode for each share

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• discount_percent_off read-only

  Compute the final checkout total after stacked percentage discounts, a fixed coupon, and a tax assumption. Sequential discounts are NOT additive.

  Parameters:

  • originalPrice (required) — number — Original price
  • coupon — number — Fixed coupon applied after all discounts
  • taxPct — number — Tax percent
  • discount1 — number — First discount percent (0-100)
  • discount2 — number — Second discount percent (0-100)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• bmi read-only

  Calculate body mass index and category from weight and height in US units.

  Parameters:

  • weightLb (required) — number — Weight in pounds
  • heightFt (required) — number — Height feet
  • heightIn — number — Additional height inches

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• bmr_tdee read-only

  Estimate basal metabolic rate (Mifflin-St Jeor) and total daily energy expenditure from age, weight, height, sex, and an activity multiplier.

  Parameters:

  • sex (required) — string — Biological sex
  • age (required) — number — Age in years
  • weightKg (required) — number — Weight in kilograms
  • heightCm (required) — number — Height in centimetres
  • activity (required) — number — Activity multiplier (e.g. 1.4)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• mortgage_payment read-only

  Estimate the full monthly housing payment (principal, interest, tax, insurance, PMI, HOA) and the total interest over the term. Requires a positive home price.

  Parameters:

  • price (required) — number — Home price
  • apr — number — Annual interest rate percent
  • hoa — number — Monthly HOA fee
  • pmi — number — Annual PMI rate percent (monthly cost = loan x rate / 12, so 0.5 on a $300,000 loan is $125/month)
  • tax — number — Annual property tax
  • down — number — Down payment
  • term — number — Loan term in years (default 30)
  • insurance — number — Annual home insurance

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• auto_loan read-only

  Estimate a monthly auto-loan payment from price, down payment, trade-in, term, and APR.

  Parameters:

  • price (required) — number — Vehicle price
  • apr — number — Annual interest rate percent
  • down — number — Down payment
  • term — number — Loan term in months (default 60)
  • trade — number — Trade-in value

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• compound_interest read-only

  Grow a balance with compound interest and optional monthly contributions. Returns future value, total contributed, and interest earned.

  Parameters:

  • principal (required) — number — Starting amount
  • rate — number — Annual interest rate percent
  • years — number — Term in years (default 10)
  • timing — string — When contributions are added
  • contrib — number — Monthly contribution
  • compound — number — Compounds per year (default 12)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• savings_growth read-only

  Project the future value of a lump-sum investment (optionally with monthly additions), including interest earned.

  Parameters:

  • amount (required) — number — Starting amount
  • rate — number — Annual interest rate percent
  • years — number — Term in years
  • contribMonthly — number — Monthly addition

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• simple_interest read-only

  Compute simple interest, total value, and a comparison to annual compounding.

  Parameters:

  • principal (required) — number — Principal
  • rate (required) — number — Annual rate percent
  • years (required) — number — Term in years

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• calorie read-only

  Estimate BMR and total daily energy expenditure using Mifflin-St Jeor, from weight/height in US units.

  Parameters:

  • weightLb (required) — number — Weight in pounds
  • heightFt (required) — number — Height feet
  • age — number — Age in years
  • sex — string — Biological sex
  • activity — number — Activity multiplier (e.g. 1.2)
  • heightIn — number — Height inches

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• percentage read-only

  Solve percentage problems: what is X% of Y, X is what % of Y, or the % change from X to Y.

  Parameters:

  • val1 (required) — number — First value
  • val2 (required) — number — Second value
  • mode — string — Calculation mode (default of)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• square_footage read-only

  Compute total area (and with-waste area) from up to two rectangular spaces, plus square yards, square metres, and acres.

  Parameters:

  • length (required) — number — First space length
  • width (required) — number — First space width
  • waste — number — Waste percent
  • width2 — number — Second space width
  • length2 — number — Second space length

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• apy read-only

  Compute annual percentage yield from a nominal rate and a compounding frequency, plus the one year interest and ending balance on an example deposit.

  Parameters:

  • rate (required) — number — Nominal interest rate percent
  • deposit (required) — number — Example deposit amount
  • compound (required) — number — Compounding periods per year (e.g. 12 for monthly)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• win_loss_percentage read-only

  Compute a winning percentage from wins, losses, and ties, where ties count as half a win.

  Parameters:

  • wins (required) — number — Games won
  • losses (required) — number — Games lost
  • ties — number — Games tied (default 0)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• slope read-only

  Compute slope from rise and run as degrees, percent grade, and the rise to run ratio. Run must be above zero.

  Parameters:

  • rise (required) — number — Vertical rise
  • run (required) — number — Horizontal run, above zero

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• rule_of_72 read-only

  Estimate the doubling time of money at a fixed rate using the rule of 72, plus the exact doubling time from the compound formula. Rate must be between 0 and 30 percent.

  Parameters:

  • rate (required) — number — Annual growth rate percent (0 to 30)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• cagr read-only

  Compute the compound annual growth rate connecting a starting and an ending value over a number of years, with total return percent and absolute change.

  Parameters:

  • start (required) — number — Starting value, above zero
  • end (required) — number — Ending value, zero or more
  • years (required) — number — Number of years, above zero

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• remainder read-only

  Compute the remainder and floored quotient of a division. Works for decimal inputs, not just integers.

  Parameters:

  • a (required) — number — Dividend
  • b (required) — number — Divisor, not zero

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• combinations read-only

  Compute the number of distinct combinations, n choose r, using a multiplicative form that avoids factorial overflow.

  Parameters:

  • n (required) — number — Total items, at least 1
  • r (required) — number — Items chosen, between 0 and n

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• margin_of_error read-only

  Compute the margin of error for a survey sample at the 90, 95, or 99 percent confidence level, assuming maximum variance proportions.

  Parameters:

  • n (required) — number — Sample size, above zero
  • confidence — string — Confidence level percent (default 90)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• va_mortgage read-only

  Monthly VA loan payment including the funding fee, with no PMI. Returns the financed amount, payment, and total interest.

  Parameters:

  • principal (required) — number — Loan principal
  • apr (required) — number — Annual interest rate percent
  • term (required) — number — Loan term in months
  • fee — number — VA funding fee percent (default 0)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• gross_rent_multiplier read-only

  Gross rent multiplier for a rental property: price divided by annual gross rent. Lower means more rent per dollar of price.

  Parameters:

  • price (required) — number — Property price
  • rent (required) — number — Monthly rent

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• emergency_fund read-only

  Emergency fund target (expenses times coverage months), the remaining gap versus current savings, and months to close the gap at a fixed monthly contribution.

  Parameters:

  • expenses (required) — number — Monthly core expenses
  • months (required) — number — Coverage target in months
  • saved — number — Current savings (default 0)
  • monthly — number — Monthly contribution (default 0)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• dividend_reinvestment read-only

  Compound a portfolio with a constant dividend yield and price growth, reinvesting monthly and optionally adding deposits. Returns ending value, total contributed, and dividends reinvested.

  Parameters:

  • initial (required) — number — Starting investment
  • yieldPct (required) — number — Dividend yield percent (the key yield is also accepted)
  • growth (required) — number — Annual price growth percent
  • years (required) — number — Holding period in years
  • contribution — number — Monthly deposit (default 0)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• budget_50_30_20 read-only

  Split monthly after-tax income by the 50/30/20 rule into needs, wants, and savings or debt paydown.

  Parameters:

  • income (required) — number — Monthly after-tax income

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• growing_degree_day read-only

  Accumulate growing, heating, or cooling degree days (Fahrenheit basis) from daily high, low, a base threshold, and a day count. Includes Celsius-basis totals.

  Parameters:

  • tmax (required) — number — Daily high in Fahrenheit
  • tmin (required) — number — Daily low in Fahrenheit
  • base (required) — number — Base threshold in Fahrenheit
  • days (required) — number — Number of days (1 to 366)
  • mode — string — Degree day mode (default gdd)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• insulation read-only

  U-value of an insulation upgrade and an estimated annual heating saving from conduction, using heating degree days, area, kWh conversion, and utility cost.

  Parameters:

  • r1 (required) — number — Current R-value
  • r2 — number — Upgraded R-value (defaults to current)
  • area — number — Area in square feet
  • cost — number — Utility cost in dollars per kWh (0 disables the dollar estimate)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• roofing read-only

  Roof area from footprint and pitch, with waste allowance, roofing squares, and approximate shingle bundles (3 per square).

  Parameters:

  • length (required) — number — Footprint length in feet
  • width (required) — number — Footprint width in feet
  • rise — number — Pitch rise per 12 run (default 0)
  • waste — number — Waste percent (default 0)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• maintenance_calories read-only

  Daily maintenance calories (TDEE) from Mifflin-St Jeor BMR and an activity level, using metric inputs.

  Parameters:

  • sex (required) — string — Biological sex
  • age (required) — number — Age in years (10-90)
  • weightKg (required) — number — Weight in kilograms (30-350)
  • heightCm (required) — number — Height in centimetres (120-230)
  • activity (required) — number — Activity level index 0-4: 0 sedentary, 1 light, 2 moderate, 3 very active, 4 extra active

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• protein_molecular_weight read-only

  Estimate a protein chain molecular weight in Da and kDa from residue count and average residue mass, plus peptide bond count.

  Parameters:

  • residues (required) — number — Number of amino acid residues (1-100000)
  • avgResidueMass (required) — number — Average mass per residue in Da (e.g. 110)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• key_transposition read-only

  Transpose a musical key and report the number of semitone steps upward between two keys.

  Parameters:

  • fromKey (required) — string — Original key (default C)
  • toKey (required) — string — Target key (default C)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• audio_time_stretch read-only

  Compute the new duration of audio at a playback speed, plus the percent time change.

  Parameters:

  • duration (required) — number — Original duration in seconds
  • speed (required) — number — Playback speed multiplier (e.g. 1.25)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• youtube_revenue read-only

  Estimated YouTube Adsense revenue from monthly views and RPM, with an annual figure and a 30 percent RPM swing range. RPM defaults to 2 when omitted.

  Parameters:

  • views (required) — number — Monthly view count
  • rpm — number — Revenue per mille in dollars (default 2)

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• ceiling_tile read-only

  Count 2x2 ft ceiling tiles needed for a rectangular room, with room area and a 5 percent cut-waste reminder.

  Parameters:

  • length (required) — number — Room length in feet
  • width (required) — number — Room width in feet

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• boat_loan read-only

  Boat or RV loan payment with optional sales tax, down payment, and trade-in, including amount financed and total interest.

  Parameters:

  • price (required) — number — Boat price
  • apr (required) — number — Annual interest rate percent
  • term (required) — number — Loan term in whole months (1-600)
  • down — number — Down payment
  • trade — number — Trade-in value
  • taxPct — number — Sales tax percent

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• pressure read-only

  Compute pressure in Pascals, kilopascals, and psi from a force in newtons over an area in square metres.

  Parameters:

  • force (required) — number — Force in newtons
  • area (required) — number — Area in square metres

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

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