Changelog
Every calculator added, formula changed and figure corrected on BuildCalculators — dated, and published rather than fixed quietly.
If a number on this site is wrong, we would rather correct it in public than have you keep using it. Corrections appear here with the date and what changed, so anyone who relied on an earlier figure can see that it moved.
Log
- AddedA live scale model on the Concrete Calculator. Below the tool, an isometric drawing of the slab, footing or columns redraws to your dimensions as you type, with the order shown as a stack of 80 lb bags. The bag count is computed by the same tested function as the result panel, so the picture can never disagree with the number.
- AddedEvery calculator can now be embedded on other sites. Each calculator page has a copy-paste snippet that drops an auto-sizing, always-current version of the tool into any page, with a credit link back to the full calculator as the condition of use.
- AddedThe guides section, with five launch guides: concrete slab cost per square foot, asphalt versus concrete driveways, how to calculate concrete for a slab, gravel driveway cost, and roof replacement cost by material. Every figure matches the ranges already published on the calculators, and each guide links into the tools that run the arithmetic.
- AddedFull guides on the Square Footage and Cubic Yard calculators: worked examples with the arithmetic shown, coverage and weight reference tables, 2026 cost context and the mistakes that actually happen. Both pages previously carried only the tool and its FAQ.
- FixedBag and unit counts could read one too high. 192 ft³ × 1.1 ÷ 0.6 evaluates to 352.00000000000006 in floating point, and rounding up turned an exact 352 into 353. Counts are now collapsed to six decimals before rounding up. Affected the concrete bag count most visibly.
- ChangedThe Sealcoating Calculator now defaults to an average surface (70 ft² per gallon) rather than smooth (80). Most driveways being sealed are average or worse, and the smooth figure under-orders by about 20% — the exact mistake the page warns about.
- AddedConcrete Slab Cost, Rebar and Board Foot calculators. Phase one is complete: 15 calculators across five categories, every published figure checked against the engine on each build.
- CorrectedA slab cost example showed $1,251 for 7.82 yd³ of ready-mix. That used the rounded volume; the correct figure from the unrounded value is $1,252.
- AddedAsphalt Tonnage, Asphalt Driveway Cost and Sealcoating calculators. All five categories now have live tools and are indexed.
- AddedRoofing Calculator, Roof Pitch Calculator and Roof Replacement Cost Calculator, with the full pitch multiplier table. The Roofing category is now live.
- CorrectedThree cost examples on the Roof Replacement Cost Calculator were rounded to the nearest ten dollars, which disagreed with the calculator’s own output. They now show the exact figures the tool produces.
- AddedGravel, Crushed Stone and Mulch calculators, with compaction allowances and density by material. The Aggregates & Materials category is now live.
- CorrectedA worked example on the Concrete Calculator showed 1.52 yd³ for a 40 ft footing at 15% waste. That figure rounded an intermediate step; the correct result is 1.51 yd³. Every published worked example is now checked against the engine on each build.
- AddedMethodology, sources and changelog pages. Every constant used by the calculators is now published with its origin, generated from the same module the calculators import.
- AddedConcrete Calculator (slab, footing and column modes), Square Footage Calculator and Cubic Yard Calculator. Ten formula assertions covering every constant.
- AddedCategory hubs for concrete, asphalt, aggregates, roofing, and area and volume. Hubs without a live calculator are excluded from search results until they have one.
Found an error?
Tell us via the contact page — include the calculator name and the inputs you used, which makes it far quicker to reproduce. Confirmed corrections are logged here and the fix ships the same day where we can.
How constants are chosen and guarded is on the methodology page.