We design calculators from a simple principle: start with the rand amount, show the estimated outcome, and reveal technical assumptions only when needed.
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 use a monthly contribution and illustrative compound interest. Home-loan principal is calculated using the present value of monthly instalments.
Why the numbers are examples
Utility prices vary by supplier, user category, region and time. Savings returns and mortgage interest rates depend on financial products and risk. We use explicitly labelled example rates so the tool can work immediately, but we do not imply they are live market prices.
What we do not model
Many calculators simplify taxes, standing charges, usage patterns, installation costs, equipment losses, lender assessments and variable prices. Page-level notes explain the most important exclusions. Actual costs may be materially different.
Privacy-first calculations
Inputs and arithmetic take place in the browser; this build does not have a calculator data backend.
Reviewed: 13 October 2026.
Calculation spot-checks
We test the arithmetic behind everyday results with simple check cases, including zero-growth savings, negative remaining budgets, electricity unit conversion and the reverse-loan formula. New assumptions are not presented as official rates unless a dated supplier source can be verified and credited.
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 change the calculation formula or turn a hypothetical result into a product recommendation.
Corrections and updates
Calculator models are simplifications. Material bugs should be corrected and dates updated when substantive content or assumptions change. 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 adds an illustrative fee and two energy blocks but does not reproduce a specific municipality's billing engine.
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. Deposits may be added to show a simple purchasing-price scenario; 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, revisions and quality controls
Draft text and software development may be supported by AI tools. Automated checks examine page structure, internal links and sample calculator outputs, but they cannot establish that an illustrative market rate is current or that a particular result suits a reader's circumstances. Substantive changes should be checked for arithmetic, limitations and primary-source support. We update review dates when content materially changes, not merely to make an article appear newer.