Changelog

Changes to the calculators and pages, newest first. Each calculator page also shows the date its content last changed.

2026-10-08: grass seed, rainwater tanks, fence runs and roof sections

New grass seed calculator: new lawn, overseeding or patch repair, seeding rates for 11 grass types and blends from university extension guides (or your label rate), a shade mix for shaded areas, extra seed on slopes, and real bag sizes.
New rainwater tank size calculator: roof catchment, 12 months of rainfall (paste a row of values), indoor and garden use, a month-by-month balance chart and table, a dry-spell buffer, and standard tank and barrel sizes in gallons or litres.
Fence calculator: several runs joined at corners or as a loop, gates with their width, corner, end, gate and line posts, sloped runs (racked or stepped), concrete per hole from the post hole math, and a fuller shopping list.
Shingle calculator: roof sections with their own pitch and shape, plus starter strip, hip and ridge cap, drip edge, valley lining and nails from the edge lengths, with editable coverages.

First visits pick units and currency from your approximate country as well as your browser language, with no permission prompt. The rainfall button names your approximate city.
“What's it for?” chips on depth, thickness and diameter fields, each with a one-line reason and its source.
Product pickers: Owens Corning Duration and GAF Timberline HDZ shingle lines, Holland, block-paving and 600 × 600 mm paver sizes, common tile sizes, “box covers” tile boxes, and actual lumber sizes from PS 20 for deck boards, pickets and posts. Each has an “other” option.
A length × width “Measure it” helper on the sod, grass seed, insulation and rainwater roof fields.
Concrete steps from the total height, with the IRC riser and tread limits as guidance.
Post holes: “Suggest hole size from my post” using Quikrete's rule of thumb. The frost depth is never filled in.
Rooms: wall heights, room sizes, editable door and window sizes, several rooms on the drywall calculator, and paint coverage and coat chips from the label ranges.
More measurements carry over: deck piers to post holes, retaining wall to drainage gravel (both zones), drywall net wall area to insulation, and post holes to concrete bags. New Deck and Retaining wall project flows. Fixed a broken energy.gov source link on the insulation page.

First visits from the UK, Ireland, Australia and New Zealand open in metric, with the local currency symbol. A saved choice always wins, and the currency can be changed under “Prices and costs”.
Home page: “What are you building?” project tiles that open the calculators in order with the measurements carried over, a Popular row and a filter box.
Costs: estimates in whole currency units, plus optional delivery, markup and tax adding up to a total. The concrete slab calculator has a thickened-edge option.
Paver calculator: a mortar-bed option for paving slabs (sharp sand and cement, bulk bags). Mulch, gravel, topsoil, sand and paver areas can be circles or triangles.
Paint calculator: which cans or tins to buy, and separate wall and ceiling quantities.
Native share sheet on phones, a copy confirmation, an optional job name for print and copy, a “Restored your last inputs” notice, quantities on project list items, and larger Next step links.
Per-page “Checked against” tables and last-updated dates, and this changelog.

On phones, results come before the diagram, with a mini result bar that stays in view while you edit.
Invalid or empty fields are highlighted and results pause instead of showing stale numbers. Feet-and-inches entry such as 12' 6".
Store units: paver base in tons and bags, sand and polymeric sand bags, pallets, gravel bags, fast-setting post mix, and ready-mix order rounding with a bags-or-truck note.
“+ Another area” on area calculators, dimensions carried to the next calculator, and a named, grouped project list with totals. One-page print.

25 calculators with formula tests and cross-checks against other published calculators.
Every calculator page gained measuring steps, the formula, worked examples, reference tables, an FAQ and cited sources.