Formula Library
A compact index of the core formulas that appear across calculators and learning pages on Plain Figures.
Why this page exists
Formula-first sites become easier to trust when the core identities are collected in one place. This page is a plain-language reference layer for readers who want the underlying structure without opening multiple guides.
It also helps clarify that many calculators differ less in their arithmetic than in their assumptions, constraints, and interpretation rules.
Core formulas covered on Plain Figures
The main recurring formulas include amortisation for loans and mortgages, future value for compounding and savings goals, present value for protection and valuation framing, gross-to-net deduction structures, and expected-loss aggregation for risk models.
Where a calculator uses a simplified model, we say so. Where a page uses a benchmark convention rather than a legal or regulatory definition, we say that too.
- Amortisation: level-payment loans and mortgages
- Future value: savings, investing, and retirement projections
- Present value: protection and replacement-value framing
- Expected loss: probability x severity scenario work