io.github.vladimirwrites/nestegg-calculators

Monthly loan amortization schedule and summary. Supports dated extra principal payments and a rate-fixed period. detail controls output size: 'summary' (default) returns totals plus a per-year breakdo…

Time and interest saved by paying a fixed extra amount every month on a loan, versus the baseline schedule.

Future value of a single lump sum compounded annually.

Future value of a fixed monthly contribution, optionally stepping up each year.

Compound annual growth rate between two values over a number of years. Returns a decimal (0.07 means 7%).

Fraction of income saved (savings divided by income). Returns a decimal.

Convert an amount using a rate supplied by the caller (units of target currency per unit of source). No rate is ever looked up.

Value after compounding down (or up) at a yearly percentage rate over a number of years. This is the method the app uses for long-term assets.

Straight-line depreciation: value falling evenly to a salvage value over a useful life.

FIRE target nest egg from annual spend and a safe withdrawal rate (default 4%), plus the gap from today and the years to reach it given optional savings and growth. No advice.

Inverse of contributions: the fixed monthly amount needed to reach a target future value over a number of months, given an optional starting balance.

Convert a nominal amount to today's purchasing power (real), or with toNominal inflate a real amount forward, at a given annual inflation rate.

Convert a nominal annual rate to the effective annual rate (APY) for a compounding frequency, or with toNominal recover the nominal rate from an APY.

Net present value of a cashflow series (index 0 is today; outflows negative) discounted at a per-period rate.

Internal rate of return: the per-period rate that zeroes the NPV of a cashflow series. Returns a percent, or null when the series never crosses zero.

Refinance break-even: monthly saving, whole months to recoup closing costs, and (if remainingMonths given) the net saving over the remaining term.

Months of runway: liquid savings divided by monthly expenses.

Maximum loan and home price the income supports: the DTI cap on gross monthly income (less existing debts) sets the payment, whose present value at the rate and term is the loan.

Multi-debt payoff plan under a fixed monthly budget. method 'avalanche' (highest rate first) minimizes interest; 'snowball' (smallest balance first) clears accounts soonest. Returns months, total inte…

How many years a balance lasts while withdrawing from it: the balance grows each year, then the withdrawal (optionally stepping up) is taken. Returns the depletion year, or sustainable=true when it ou…

Present value of a single future amount discounted annually. The inverse of future-value.

Annual return needed to grow a starting value to a target over a number of years, optionally with a fixed annual contribution. With no contribution this equals CAGR. Returns a percent, or null when un…

Bond yield to maturity: the nominal annual yield that prices a bond at the given price, with periodic coupons and face returned at maturity. Solved numerically. Returns a percent, or null.

Progressive tax from caller-supplied brackets. No jurisdiction, year, or rates are baked in: pass the brackets yourself. Returns total tax, effective rate, and marginal rate.

Convert between margin and markup. Supply any one of cost/price plus one of marginPct/markupPct (or both cost and price); returns cost, price, profit, marginPct, and markupPct.

Compound growth at any frequency, with an optional contribution each period (paid at period end). Generalizes future-value (periodsPerYear 1) and contributions (periodsPerYear 12).

German net (Netto) salary from gross (Brutto). No tax tables are baked in: look up the current year's statutory figures and pass them in. Income tax (Lohnsteuer) and Soli are amounts; church tax is a …

Exact German net (Netto) salary from annual gross (Brutto) for tax years 2023-2026. Income tax and Soli follow the official BMF Programmablaufplan for the year (to the euro; 2024 uses the retroactive …

German flat tax on capital income (Abgeltungsteuer, §32d EStG) for tax years 2023-2026 with the year's Sparerpauschbetrag built in. 25% above the allowance, Soli 5.5% on top (no Freigrenze for capital…

German child benefit (Kindergeld) for 2023-2026: the year's flat monthly amount per child (uniform since 2023), as monthly and annual totals.

German Midijob / Uebergangsbereich (paragraph 20 Abs. 2a SGB IV) for 2023-2026: classifies a monthly pay as Minijob / Midijob / regular against the year's thresholds and, inside the Midijob band, comp…

German pension points (Entgeltpunkte, paragraph 63 SGB VI) for 2023-2026: points earned from an annual gross via the year's Durchschnittsentgelt (capped at the contribution ceiling), the aktueller Ren…

Value-added tax (MwSt/USt, sales tax) on a price. By default adds the tax to a net price; with inclusive=true treats the amount as gross and extracts the tax. The rate is always an input (19 or 7 for …

Return on investment: total percent gain, plus the annualized rate when a holding period in years is given.

Real (inflation-adjusted) return from a nominal rate via the Fisher relation: (1+nominal)/(1+inflation) - 1.

Mean, sample variance, and sample standard deviation (n-1) of a series of returns. Pass percents to get a percent stdev (volatility).

Sharpe ratio: excess mean return per unit of volatility, (mean - riskFree) / stdev. Null when volatility is undefined or zero.

Maximum drawdown of a value series: the largest peak-to-trough decline, as a positive percent.

Holding-period return: (income + capital gain) / starting value, in percent.

Effect of an annual fee: the compounded balance at the gross rate vs net of the fee, and the amount lost to fees.

Dollar-cost averaging: buying a fixed amount each period at the given prices. Returns units accumulated, total invested, average cost, and final value at the last price.

Price of a coupon bond given a yield: present value of the coupons plus the face at maturity.

Current yield: the annual coupon as a percent of the bond's current price.

Macaulay duration (PV-weighted average time of cashflows, in years) and modified duration (price sensitivity to yield).

Bond convexity (years^2): the curvature of price with respect to yield, used alongside duration.

Price of a zero-coupon bond: face value discounted to today at the yield.

Accrued interest since the last coupon: the annual coupon pro-rated by days elapsed over the day-count basis.

Black-Scholes price of a European call or put option, plus d1/d2. Volatility and rates in percent; optional continuous dividend yield.

Black-Scholes greeks for a European option: delta, gamma, vega (per 1% vol), theta (per day), rho (per 1% rate).

Put-call parity: given one option price, returns both. Provide call or put, plus spot, strike, years, and the rate.

Break-even underlying price at expiry: strike + premium for a call, strike - premium for a put.

Split an option premium into intrinsic value (in-the-money amount) and time value.

Present value of an ordinary annuity (level payment at each period end). rate is the per-period rate in percent.

Future value of an ordinary annuity. rate is the per-period rate in percent.

The level payment that amortizes a present value over n periods (the loan-payment formula). rate is per period.

Present value of a level or growing perpetuity: payment / (rate - growth). Null when growth is not below the rate.

Years to double: the rule-of-72 estimate (72/rate) and the exact figure (ln2 / ln(1+rate)).

Simple payback period: periods until cumulative cashflows recover the initial cost, interpolated within the crossing period. Null if never.

Discounted payback period: like payback-period but each cashflow is discounted at the per-period rate.

Modified internal rate of return: negatives financed at financeRate, positives reinvested at reinvestRate. Percents in and out.

Date-aware net present value: each amount discounted by its fractional years (act/365) from the first cashflow's date. Annual rate in percent.

Date-aware internal rate of return: the annual rate that zeroes the XNPV of irregular dated cashflows. Null if no rate fits.

Effective APR including upfront fees: the note-rate payment priced against the net proceeds (amount - fees). Annual percent.

Interest-only monthly payment on a balance.

Balloon loan: payment based on a long amortization, with the balloon being the balance still due after the shorter balloon term.

Loan-to-value ratio, percent (loan / property value).

Debt-to-income ratio, percent (monthly debt / gross monthly income).

Months to clear a credit-card balance at a fixed monthly payment, plus interest paid. Null when the payment can't cover the first month's interest.

Mortgage points break-even: the upfront cost to buy down the rate, the monthly payment saving, and the whole months to recoup it.

Biweekly mortgage acceleration: paying half the monthly payment every two weeks. Returns the biweekly payment and the months and interest saved.

Capitalization rate: net operating income as a percent of property value.

Cash-on-cash return: annual pre-tax cash flow as a percent of the cash invested.

Net operating income: gross rental income less vacancy and operating expenses.

Gross rent multiplier: price divided by gross annual rent.

Debt service coverage ratio: net operating income divided by annual debt service.

Weighted average cost of capital: equity and after-tax debt weighted by the capital structure. Percents in and out.

Break-even volume: fixed costs divided by the per-unit contribution (price - variable cost), plus the revenue at that volume.

Contribution margin per unit and as a percent of price.

Current ratio: current assets over current liabilities.

Quick (acid-test) ratio: (current assets - inventory) over current liabilities.

Return on equity, percent: net income over shareholders' equity.

Return on assets, percent: net income over total assets.

Declining-balance depreciation: a fixed percent of the reducing book value, for a given year. Returns that year's depreciation and the remaining book value.

Double-declining-balance depreciation: 2/usefulYears of the book value each year, not falling below salvage.

Sum-of-the-years'-digits depreciation: the depreciable base weighted toward the early years.

Units-of-production depreciation: the depreciable base spread over total expected units, charged by the units used this period.

Net worth: assets minus liabilities.

The 50/30/20 budget split of monthly income into needs, wants, and savings.

Tip and split: the tip amount, the total, and the per-person share.

A single percentage discount: the amount off and the final price.

Stacked discounts applied in order: the final price and the effective single discount rate.

Percentage change from one value to another. Null when the starting value is zero.

Unit price: price divided by quantity (for comparing pack sizes). Null when quantity is zero.

Annualize an hourly rate (and the monthly equivalent).

Hourly rate implied by an annual salary.

After-tax yield: a yield reduced by the tax rate. Percents in and out.

Tax-equivalent yield: the taxable yield that matches a tax-free (e.g. muni) yield. Percents in and out.

Coast FIRE: whether the current nest egg, left to grow untouched to retirement, already reaches the FIRE target. Returns the target, the projected balance, whether it coasts, and any shortfall.

Barista FIRE: the nest egg needed when part-time income covers part of the spending, so the portfolio only funds the remainder at the safe withdrawal rate.

Inputs, outputs, formula, and rounding for every calculator.

Agent-oriented index of the calculators and API.

Plan or review a mortgage repayment.

Check progress toward financial independence.

Estimate a German net (Netto) salary.