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PRACTICAL HOME PROJECT MATH

Project budget calculator

Combine known costs and a contingency allowance without hiding the assumptions.

Tax is applied only to materials in this simplified model. Enter your own applicable rate. Contingency is a planning allowance, not a forecast.

YOUR PLANNING ESTIMATE

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Enter your measurements

See the calculation

Separate known costs from allowances

Enter quoted or researched materials, labor and delivery costs. Add other known items to the third field. Avoid treating an unquoted item as zero simply because you do not yet know the price; keep it on a separate question list.

The calculation

Subtotal = materials + labor + delivery/other + tax on materials. The planning total adds the selected contingency percentage to that subtotal. The tax field is deliberately limited to materials; it does not determine which charges are taxable for your project.

A worked example

$1,000 of materials, $800 of labor and $100 of other costs make a $1,900 subtotal when the tax field is zero. A 10% contingency adds $190 for a $2,090 planning total.

Use the result as a working budget

A contingency is money you choose to allow for uncertainty. It is not a prediction or a quote. Update the inputs when the scope changes, and confirm the actual taxes, fees and payment terms with your providers.