Money math, demystified
Finance
Tips, loans, savings and growth projections built on standard formulas. Transparent arithmetic — projections, never financial advice.
Tip Calculator
Tip, total and per-person split with quick presets and a visual bill breakdown.
Discount Calculator
Sale price from percent-off, stacked codes and tax — with the exact amount saved.
Fuel Cost Calculator
Fuel a trip burns and what it costs — round trip and per-person split included.
Electricity Cost Calculator
What any appliance costs to run — per day, per month and per year, from watts and your tariff.
EV Charging Cost Calculator
What a charging session costs and how far it takes you — from pack size, your tariff and the charger's losses.
Water Heating Cost Calculator
What one shower, bath or tank of hot water costs — and what it adds to the monthly bill.
Gas Heating Cost Calculator
What it costs to keep your home warm — heat load, gas use and the daily, monthly and seasonal bill.
EV vs Petrol Cost Calculator
Monthly costs of an electric car against a petrol one — savings, per-km rates and the break-even tariff.
Heat Pump vs Gas Calculator
The same year of heat priced on both meters — gas boiler against heat pump, with the break-even tariffs.
Solar Panel Payback Calculator
Net cost, year-1 savings and simple payback for a rooftop PV system — with lifetime returns and LCOE.
Compound Interest Calculator
See what compounding itself does to a balance — annual, monthly or daily — and what APY a nominal rate actually pays.
Loan Calculator
Fixed-rate loan payment, total interest and payoff time — with extra-payment savings.
Mortgage Calculator
Mortgage payment, lifetime interest and payoff — with extra payments and a yearly schedule.
ROI Calculator
Return on investment as a percentage and absolute gain or loss.
Savings Calculator
Work out what a starting balance plus a fixed monthly deposit becomes in a savings account, with interest shown separately from your own deposits.
Investment Calculator
Project a portfolio from a lump sum plus regular contributions at an expected return — with the inflation-adjusted value in today’s money and the effective CAGR.
Retirement Calculator
See what your savings could be worth at retirement, what yearly income that supports at your chosen withdrawal rate, and how far you are from a target income.
Freelance Hourly Rate Calculator
The hourly and day rate that covers the income you want, tax, business costs and the hours you can actually bill.
Break-Even ROAS Calculator
The return on ad spend at which an order stops losing money, the most a sale can cost in ads, and the ROAS a target margin needs.
AI API Cost Calculator
What your workload costs per month on each large language model, with prices read live from an open price list.
What this covers
Everyday money arithmetic: splitting a bill, what a loan or mortgage costs, what a balance grows into, and what a portfolio might be worth later. These are transparent calculations on the numbers you enter — every page shows its formula, and none of them is financial advice.
Which tool to use
For borrowing, the Loan and Mortgage calculators share one amortization engine; the mortgage page simply defaults to a longer term. For growing money, four tools run nearly the same arithmetic on different questions: Compound Interest is about the compounding mechanism itself, Savings about a bank balance plus a monthly deposit, Investment about a portfolio at an assumed return in today’s money, and Retirement about the income that balance supports. ROI measures a completed gain, and the Tip Calculator splits a bill. For work and business, the Freelance Hourly Rate Calculator prices your time from the income you need, the Break-Even ROAS Calculator tells an online shop how much ad spend each sale can carry, and the AI API Cost Calculator prices a language-model workload at live list prices.
Frequently asked questions
Are these projections or predictions?
Projections. They apply your assumptions consistently; they do not know what rates or markets will do. A constant annual return is a modelling convenience, not a forecast.
Is tax included?
No. The tools work on the figures you enter, before tax, fees or inflation unless a field explicitly asks for one. The investment and retirement pages do offer an inflation-adjusted view because the difference over decades is large enough to change a decision.
Why does the total interest exceed the loan amount on long mortgages?
Because interest accrues on the outstanding balance every month and early payments are mostly interest. The amortization table shows the year principal overtakes interest.