Each calculator follows the same approach: start with your budget, show an estimate and let you check or change the inputs.
Every result explains its assumptions
Electricity and appliance estimates use energy in kilowatt-hours. Petrol estimates use a price per litre and litres per 100 kilometres. Savings projections combine monthly contributions with growth at an assumed rate. Home loan estimates work backwards from a monthly repayment, interest rate and term to calculate the loan amount.
Why the numbers are examples
Electricity prices vary by supplier, tariff category, area and date. Savings returns and home loan rates depend on the product and its terms. Calculators start with labelled example rates. Where we include a published tariff, we give its source and applicable period. The tools do not fetch live prices.
What we do not model
The calculators do not account for every tax, fixed charge, usage pattern, installation cost, equipment loss or price change. They also cannot assess whether a lender will approve a loan. Each page explains its main exclusions. Actual costs may differ substantially.
Where calculations happen
Calculations run in your browser. There is no server that processes calculator inputs. If you copy a share link from the homepage, the amount is included in the link and may appear in browser history or hosting logs when it is opened.
Reviewed: 13 October 2026.
Calculation spot-checks
Checks cover page links, calculator inputs and sample results, including zero budgets, electricity units and prepaid tariff blocks. Published rates should have a dated supplier source. Passing a software test does not establish that a rate is current.
How this site makes money
These calculators are free and currently contain no advertising scripts. In the future, clearly identified advertisements or optional paid features may support the site. Commercial arrangements should not affect the formulas or make an example result a product recommendation.
Corrections and updates
Calculators simplify real costs. Errors that affect results should be corrected, and review dates updated when the content or assumptions change substantially. Always compare the estimate with current bills, contracts and official tariffs before acting.
Worked examples and formulas
Electricity: estimated kWh = rand budget ÷ assumed price per kWh. At R3.00/kWh, a R600 energy budget represents 200 kWh before any fixed charges or block pricing. At 10 kWh per day, that is about 20 days. The prepaid model subtracts the charges you enter and applies two energy rates, taking earlier monthly purchases into account. It includes a Cape Town Domestic example but cannot reproduce every supplier’s billing rules.
Petrol: litres = rand budget ÷ pump price; kilometres = litres × 100 ÷ vehicle consumption (L/100 km). At an assumed R25/litre and 8 L/100 km, R400 buys 16 litres and represents about 200 km before reserve or road-condition adjustments.
Savings: for a constant month-end contribution P over n months, with monthly rate r, future value = P × ((1 + r)n − 1) ÷ r. At zero growth we use P × n instead. For example, R1,000 monthly for 24 months is R24,000 of contributions before growth. This is a mathematical illustration, not a forecast.
Home loans: loan principal = monthly payment × (1 − (1 + r)−n) ÷ r, where r is the assumed monthly interest rate and n is the number of payments. At zero interest we use the payment multiplied by the number of months. Adding a deposit gives an estimated purchase price before buying costs; legal fees, lender eligibility and other expenses are not covered.
How readers can verify the inputs
Check an actual meter statement or approved municipal tariff before relying on energy estimates. The National Energy Regulator's decisions are a starting point, but your own supplier and tariff category determine the amount charged. For vehicle fuel prices, consult the Department of Mineral and Petroleum Resources and the price actually offered where you fill up. For home loans, compare lender quotations and read about the South African Reserve Bank's monetary policy and the National Credit Act.
AI assistance and checks
AI tools may help with draft text and software development. Automated checks cover page structure, links and sample results. Rates, source documents and the limits of each calculation still need to be checked separately. Review dates reflect substantial changes to content or assumptions.