How topics are researched
Topics start from questions people ask when making money decisions. Where a statement relies on outside data, the source is shown beside it. Where a guide only explains definitions and arithmetic, it says it cites no external statistics.
How formulas are developed
Each calculator uses a standard financial formula or a simple month-by-month simulation, both shown below. Inputs are limited to sensible ranges and entries that are blank, negative or not numbers are handled safely rather than producing errors.
How calculations are verified
Each calculator is run against a fixed set of input combinations, including zero, negative, very large and edge-case values, and the outputs are recorded. Whenever a calculator changes, the same set is run again and any difference in output must be explained before the change is published. Verification means these documented tests; it does not mean independent audit or review by a third party.
How assumptions are handled
Every calculator page lists its key assumptions beside the result. Rates of return, inflation and withdrawal rates are inputs you choose, and results should be read as “what if”, not “what will”.
How sources are handled
Where outside data is used, the preferred sources are government agencies, regulators, central banks, academic research, official financial institutions and recognised professional organisations.
Privacy of calculations
Calculations run in your browser. The figures you enter are not sent to WorthMorrow, are not placed in page addresses and are not included in analytics.
Calculator formulas
Compound Interest Calculator
Balance grows each period by r ÷ n, with deposits added monthlySimplifications: a constant rate; no fees, taxes or inflation; for quarterly and annual compounding, deposits earn interest only from the next compounding date. Daily compounding has been removed. The available frequencies are monthly, quarterly and annual.
Financial Freedom Calculator
Target = annual spending ÷ withdrawal rate; time = months until balance (plus monthly savings and monthly-equivalent return) reaches the targetSimplifications: constant spending, savings and returns; no taxes, pensions or other income; the search is capped at 100 years.
Debt Payoff Calculator
Monthly interest = balance × APR ÷ 12; payment minus interest reduces the balanceSimplifications: one combined balance at one average rate; fixed rate; no new borrowing or fees. If the payment does not exceed monthly interest, the balance does not fall and no payoff date is given.
Emergency Fund Calculator
Target = essential monthly costs × months of coverSimplifications: only essential costs count; insurance and outside support are not netted off; the yield is for illustration only.
Net Worth Calculator
Net worth = total assets − total liabilitiesSimplifications: values are the ones you enter; no tax on sale; negative or non-numeric entries are ignored.
Savings Rate Calculator
Employee savings = P + S; gross rate = (P + S + M) / (G + M); after-tax-income rate = (P + S) / (G − T); saved per month = P + S + M; annual employee savings beside Band = (P + S) × 12G = gross income, T = taxes, P = pre-tax employee contributions, S = post-tax contributions, M = selected employer match, D = additional debt principal. Rates above are multiplied by 100 for percentages. Take-home cash pay = G − T − P; no other payroll deductions are modeled. Wealth-building allocations = P + S + D + M, not realized net-worth growth.
Investment Return Calculator
Annualised return = ((ending value + income) ÷ starting value)^(1 ÷ years) − 1One lump sum, no external contributions or withdrawals. Add only distributions not already included in ending value, assumed received at period end. Use fees and taxes consistently. Real annualized return = (1 + nominal annualized return) / (1 + annual inflation) − 1. Starting value and holding period must be positive. A total loss is reported with an explanatory message, not annualized output. Future portfolio tools may use TWR (geometrically linked subperiod returns) and MWR/XIRR (dated investor cash flows); neither is implemented here.
Cash flow and net worth
A cash-flow surplus is money remaining after recorded outflows, not automatically actual saving. Saving and investment contributions reflect money retained or allocated; debt principal reduces liabilities; net-worth change also includes asset-price changes and other valuation movements.
How updates are made
Articles and calculators show the date they were last updated. Changes to a formula are tested as described above before they are published.
How corrections are handled
If you find an error, tell us through the contact page. Confirmed errors are corrected and the change is noted on the page with its date.
Education and advice
Results are estimates for learning and planning. They are not personal advice. See the financial disclaimer and the editorial standards.