DIY Cost HQ is a collection of free calculators for homeowners and DIYers. Estimate fence and deck costs, concrete, paint, septic systems, firewood, generator sizing, and solar systems — no signup, no fees.
Every tool on this site produces planning estimates, not professional advice. Prices vary by region and change over time; ratings and capacities come from manufacturers and public sources. Always verify critical numbers — vehicle ratings, electrical loads, structural spans, tax incentives — against the official source or a licensed professional before acting on them.
Every calculator here runs on inputs you control: dimensions you measure, materials you pick, and — most importantly — prices you can override with your own local numbers. The default figures are 2026 U.S. national averages drawn from retailer pricing, quarry and supplier rate sheets, manufacturer sizing guidance, and published industry data (solar pricing references SEIA/Wood Mackenzie figures; system sizing follows the same derate method installers use and NREL's PVWatts documents). Each tool shows its formula or its assumptions on the page: waste and compaction factors on the material calculators, starting-versus-running watts on the generator tool, the 0.80 derate on the solar sizer. If an assumption does not match your project, the honest fix is built in — change the input, not the conclusion. All math runs in your browser; nothing you type is stored or sent anywhere.
Price defaults are reviewed against current retailer and supplier pricing on a regular cycle and are labeled with their year, so you can judge their freshness yourself. Methodology — a pumping interval, a depth recommendation, a sizing rule — follows the published guidance of the relevant trade and extension sources, and guides cite the reasoning rather than asking you to trust a bare number. When a default and your local quote disagree, believe the local quote: lumber, concrete, and labor markets are regional in ways a national average cannot see.
These tools budget projects; they do not engineer them. A septic estimate is not a permit design, a solar layout is not a structural review, and a paint estimate cannot see your walls. Permits, codes, soil, and roof condition move real prices by tens of percent. Use the numbers to plan, to compare quotes intelligently, and to spot the bid that is suspiciously low — then confirm anything structural, electrical, or septic with a licensed local professional.