Practical home planning tools
Free home energy and renovation calculators
Estimate energy costs, renovation materials, furniture fit, rug sizes, and curtains using local values, transparent formulas, and plain-language assumptions.
Planning estimates—not quotes. Your usage, measurements, and local prices determine the result.
- Use local values
- See each formula
- No account needed
How it works
From your values to a clearer estimate
A useful estimate should be easy to create and easy to inspect. Each calculator follows the same clear path.
Enter your local values
Add the measurements, usage, and price that match your home or project.
Review the estimate
See the result with its units, formula, and useful breakdown shown together.
Check the assumptions
Read what the estimate includes, then use it as a planning guide—not a professional quote.
From the guide library
Useful answers for your next home project
Read a practical answer first, then use the matching calculator with your own values and assumptions.
Space heater monthly cost
Estimate heater cost from wattage, schedule and thermostat duty cycle.
Read the guideDehumidifier IEF and cost
Understand why an efficiency rating does not replace measured runtime and local rates.
Read the guideTile waste and spare boxes
Keep cutting allowance, repair stock and box rounding separate.
Read the guideVaulted ceiling paint
Measure ceiling slopes and gable walls separately before calculating paint quantities.
Read the guide
Built for clarity
Know what is behind each estimate
Useful planning numbers need clear limits and enough context to check them. These rules guide every Watt & Wall calculator.
Formulas you can inspect
Every result shows its units, formula, assumptions, and rounding so you can understand how the estimate was produced.
Sources with context
Defaults identify their source, geography, and last-reviewed date. You can replace regional averages with your own local values.
Local calculation with clear privacy limits
No account is required. Arithmetic runs in your browser, but shareable URLs can contain inputs and third-party services may process the page address. Do not enter confidential information.
Planning aid, not a quote
Results support early planning; they are not professional advice, contractor quotes, or guaranteed savings.
Common questions
Before you use an estimate
Quick answers about scope, local values, privacy, and what each result can—and cannot—tell you.
The formulas calculate consistently from the values you enter, but the usefulness of a result depends on accurate inputs and the stated assumptions. Treat every result as a planning estimate, not an exact prediction.
Start your estimate
Ready to make a clearer estimate?
Choose a calculator, enter the values you know, and review the formula and assumptions behind the result.
No account required. Arithmetic runs in your browser, and shared URLs can include your inputs. Do not enter confidential information.