Where numbers come from
Every number a calculator uses lives in a data file with one of three labels:
- Cited: taken from a building code, a manufacturer’s spec sheet or an industry guide, with the date we last checked it.
- Unit definition: facts like 27 cubic feet in a cubic yard or 25.4 mm in an inch.
- Placeholder: a reasonable default we haven’t verified yet, such as some waste factors and pack sizes. These show a PLACEHOLDER badge everywhere they appear.
We don’t fill in numbers from memory. Our automated tests fail if a number has neither a source nor a placeholder label.
Prices
Store prices vary a lot from place to place, so we check one Home Depot store in each of eight regions and show the one for the state you pick (Pacific: San Diego, CA; Northwest: Seattle, WA; Southwest: Phoenix, AZ; Mountain: Denver, CO; South Central: Dallas, TX; Midwest: Chicago, IL; Southeast: Atlanta, GA; Northeast: Boston, MA, not checked yet). Each price links to the product we priced and shows the date we checked it. Lumber is priced per foot from the board length the store lists.
Base gravel, sand and drainage stone are usually bought in bulk, by the cubic yard, so we price them at a landscape yard in your region (Pacific: Eastman Soil & Amendments, San Marcos, CA; Northwest: Cedar Grove, Seattle area, WA; Southwest: none checked yet; Mountain: ARS Landscape Materials & Supply, Arvada, CO; South Central: Outdoor Warehouse Supply, Lewisville and Plano, TX; Midwest: The Mulch Center, Deerfield, IL; Southeast: Cummin Landscape Supply, Metro Atlanta, GA; Northeast: none checked yet), from the prices the yard posts online. Those prices are for the material only; delivery is extra, and yards charge for it by distance. The calculators also show how many half-cubic-foot bags you’d need instead, at the Home Depot price, which suits a small job or anyone without a truck.
When your region’s store or yard doesn’t list an item, we show the middle price of the regions that do, marked PLACEHOLDER. When no store we checked sells it (ready-mix concrete, Allan Block, some bag sizes), the price is a rough example, also marked. Your prices will differ: type them into the cost estimate and they’re saved in your browser.
Building codes
We use the 2024 International Residential Code (IRC), the model code most US towns adopt, sometimes with changes and sometimes an older edition. Your town’s adopted code is the one that counts, so the calculators flag code limits as checks to confirm, not guarantees. Deck span tables were copied word for word from the ICC’s published code and are verified against a checksum in our tests. A few cells in the published beam tables break the tables’ own pattern; we treat those as likely misprints and never report them as a pass.
Rounding
- Anything you buy whole (boards, bags, blocks, bundles) is rounded up after adding waste.
- Bulk gravel and sand are rounded up to the next 0.1 cubic yard; ready-mix to the next 0.25 cubic yard.
- Code checks are conservative: where the code allows interpolation we interpolate, but we never extrapolate, and where we have to pick a table column we pick the heavier case.
Waste factors
Each calculator has one waste factor you can change. It covers damaged pieces, mistakes and cuts we can’t predict. Where we can count offcuts exactly (deck boards cut to length, rebar laps, drip edge laps) we do, so the waste factor doesn’t have to.
Units
The calculators work in US units internally because the codes and products do. Switching to metric converts your inputs and the results using exact conversion factors; product names (a 2x6, an 80 lb bag) stay as sold.
What the calculators don’t do
They don’t design structures. They count materials for a simple rectangle and check a few headline code limits. Footings, ledger attachments, guards, stairs, heavy point loads, slopes, poor soils and local amendments are outside their scope. Each page says when to call a professional.
All sources
| Source | What we use from it | Last checked |
|---|---|---|
| 2024 International Residential Code, Section R105.2 (Work exempt from permit)International Code Council · building code | Permit exemptions: fences up to 7 ft, retaining walls up to 4 ft (bottom of footing to top of wall, no surcharge), detached accessory buildings up to 200 sq ft, small low unattached decks. | 2026-10-30 |
| 2024 International Residential Code, Chapter 5 (Floors): R506 and R507International Code Council · building code | Slab thickness (R506.1), base course (R506.3.2), vapor retarder (R506.3.3), deck beam spans (Tables R507.5(1)-(4)), deck joist spans and cantilevers (Table R507.6), decking joist spacing and fastening (R507.7). | 2026-10-30 |
| 2024 International Residential Code, Section R905.2 (Asphalt shingles)International Code Council · building code | Minimum slope 2:12 and double underlayment from 2:12 to 4:12 (R905.2.2); drip edge at eaves and rakes, lapped at least 2 in (R905.2.8.5). | 2026-10-30 |
| DCA 6: Prescriptive Residential Wood Deck Construction Guide (2015 IRC edition)American Wood Council · industry guide | Deck board spacing of about 1/8 in, minimum 6x6 posts for the prescriptive method, joist hanger capacities. | 2026-10-30 |
| Voluntary Product Standard PS 20-10, American Softwood Lumber Standard, Table 3National Institute of Standards and Technology · standard | Actual (dressed, dry) sizes of nominal lumber: 1x6 is 3/4 x 5-1/2 in, 5/4 boards are 1 in thick, 2x lumber is 1-1/2 in thick, 4x4 is 3-1/2 in, 6x6 is 5-1/2 in. | 2026-10-30 |
| QUIKRETE Concrete Mix No. 1101 data sheet (revised October 2022)The Quikrete Companies · manufacturer spec | Bag yields (40 lb 0.30 cu ft, 50 lb 0.375, 60 lb 0.45, 80 lb 0.60, 90 lb 0.675), mixing water per bag, minimum pour thickness of 2 in, control joints every 6 to 8 ft, fence post hole size (3x the post width, 1/3 of the post's length deep, 6 in of mix under the post). | 2026-10-30 |
| GAF Timberline HDZ shingles: specificationsGAF · manufacturer spec | 3 bundles per square, 64 pieces per square, 256 nails per square (4-nail pattern), 5-5/8 in exposure. | 2026-10-30 |
| GAF Pro-Start Starter Strip ShinglesGAF · manufacturer spec | About 120.33 linear feet of coverage per bundle. | 2026-10-30 |
| GAF Seal-A-Ridge Ridge Cap Shingles sell sheet (RESHR112-1124)GAF · manufacturer spec | 4 bundles cover 100 linear feet (25 ft per bundle) at 6-2/3 in exposure. | 2026-10-30 |
| CMHA Tech Note PAV-TEC-002-22: Construction of Interlocking Concrete PavementsConcrete Masonry & Hardscapes Association · industry guide | Minimum 4 in compacted base for patios on well-drained soils (thicker in cold or wet soils), 1 in uncompacted bedding sand, joints 1/16 to 3/16 in, base compacted in 4 to 6 in lifts, edge restraints touching at least 1 in of the paver side. | 2026-10-30 |
| Allan Block: Basic retaining wall installationAllan Block · manufacturer guide | Base trench 24 in wide and 6 in deep plus 1 in per foot of wall height for buried block (18 in wide and 4 in deep for walls under 4 ft), 12 in of wall rock behind the block, drain pipe required for gravity walls over 4 ft or poor drainage, vented every 50 ft. | 2026-10-30 |
| Allan Block AB Collection: block and cap dimensionsAllan Block · manufacturer spec | AB Classic: 8 in high, 18 in long, 12 in deep, about 1 sq ft of wall face. AB Capstone: 4 in high, 18 in long, 12 in deep. | 2026-10-30 |
| 811: the free national call-before-you-dig serviceCommon Ground Alliance · safety service | Contact 811 a few business days before digging so buried utility lines are marked, free of charge. | 2026-10-30 |
| 2024 International Residential Code, Section R403.1.3.5.3 (Support and cover)International Code Council · building code | Reinforcement in concrete cast against the earth needs at least 3 in of cover (written for footings; we use it to keep slab bars 3 in from the edges). | 2026-10-30 |
| 2024 International Residential Code, Table R608.5.4(1) (Lap splice and tension development lengths)International Code Council · building code | #4 bars lap 20 in for Grade 40 steel and 30 in for Grade 60 (written for concrete walls). | 2026-10-30 |
| 2026 Trex Decking Installation Guide, gapping requirementsTrex Company · manufacturer guide | Minimum width-to-width gap of 3/16 in between Trex boards (3/8 in recommended in heavily wooded areas). | 2026-10-30 |
| Trex Enhance decking: board dimensionsTrex Company · manufacturer spec | Enhance boards are 0.94 in thick and 5.5 in wide (Trex's UK site; the US boards are sold in the same 1x6 nominal size). | 2026-10-30 |
| Simpson Strong-Tie Deck-Drive DSV WOOD ScrewSimpson Strong-Tie · manufacturer spec | Model DSVR212R350: #10 x 2-1/2 in deck screws, 350 per package. | 2026-10-30 |
| GAF Tiger Paw Premium Roof Deck Protection data sheet (RESUL179-1224)GAF · manufacturer spec | Roll size 10 squares (1,000 sq ft, laps excluded), 48 in wide by 250 ft long. | 2026-10-30 |
| GAF Tiger Paw installation instructionsGAF · manufacturer guide | Slopes 4:12 and up: 3 in side laps and 6 in end laps. 2:12 to under 4:12: double coverage with a 22.5 in exposure. | 2026-10-30 |
| Gibraltar Building Products galvanized steel drip edge, 10 ft (model 08331), Home Depot listingThe Home Depot · store listing | Drip edge sold in 10 ft pieces. | 2026-10-30 |
| Grip-Rite 1-1/4 in 15° coil roofing nails, 7,200 per box (GRCR3DADE), Home Depot listingThe Home Depot · store listing | Coil roofing nails sold 7,200 per box. | 2026-10-30 |
| 1/2 in x 20 ft #4 rebar (REB/4/615G4/20), Home Depot listingThe Home Depot · store listing | #4 rebar sold in 20 ft sticks of Grade 40 steel. | 2026-10-30 |
| 10-gauge wire mesh, 5 ft x 10 ft sheet, 6 x 6 in spacing, Kuhlman listingKuhlman · store listing | Welded wire mesh sold in 5 x 10 ft sheets with a 6 x 6 in grid. | 2026-10-30 |
| WWR Lap Splice Requirements (The Voice, January 2021)American Society of Concrete Contractors · industry guide | Cites ACI 439.5R-18 section 6.4: lap plain welded wire mesh one grid square plus 2 in. | 2026-10-30 |
| CMHA Tech Note PAV-TEC-003-22: Edge Restraints for Interlocking Concrete PavementsConcrete Masonry & Hardscapes Association · industry guide | Rule of thumb: the base should extend beyond spiked edge restraints at least as far as the base is thick. | 2026-10-30 |
| SnapEdge paver edge restraint brochureSEK · manufacturer guide | 8 ft pieces; gravel base at least 6 in past the paved area; one spike every 2 ft for walks and patios (every 1 ft for driveways or curves) plus one at each joint. | 2026-10-30 |
| Alliance Gator Reference Guide 2025Alliance Designer Products · manufacturer spec | Polymeric sand per 50 lb bag with 2-3/8 in pavers: 65 to 85 sq ft for 1/8 to 3/8 in joints, 22 to 42 sq ft for 3/4 to 1-1/4 in joints. | 2026-10-30 |
| Outdoor Essentials Fence Calculator: Building with Pickets (2019)UFP Industries (Universal Forest Products) · manufacturer guide | Posts 8 ft on center (6 or 8 ft typical); 2 rails per section for a 4 ft fence, 3 for a 6 ft fence; posts = sections + 1 per run + 1 per gate; add 10% to the picket count. | 2026-10-30 |
| Southern Pine specification guidelinesSouthern Pine Council · industry guide | Dimension lumber is specified in standard lengths from 8 to 20 ft in 2 ft steps. | 2026-10-30 |
| ADS 4 in x 100 ft corrugated perforated pipe (04010100), Lowe's listingLowe's · store listing | 4 in perforated drain pipe sold in 100 ft rolls. | 2026-10-30 |
| Allan Block: Material estimation worksheetAllan Block · manufacturer guide | Order an extra 5% of block to cover problems during construction. | 2026-10-30 |
| Grip-Rite 2 in x 0.092 in exterior galvanized ring-shank coil nails, 1,200 per box (GRC6R92HG1), Home Depot listingThe Home Depot · store listing | Fence nails sold 1,200 per box. | 2026-10-30 |
| Paver Sand, 0.5 cu ft bag (98000), Home Depot listingThe Home Depot · store listing | Paver sand sold in 0.5 cu ft bags. | 2026-10-30 |
| Pavestone Paver Base, 0.5 cu ft bag (100580973), Home Depot listingThe Home Depot · store listing | Paver base gravel sold in 0.5 cu ft bags. | 2026-10-31 |
Calculators
- Deck Material Calculator: Boards, Joists, Beams and Screws
- Roof Pitch and Shingle Calculator: Squares, Bundles and Underlayment
- Concrete Slab Calculator for a Shed: Cubic Yards, Bags and Rebar
- Paver Patio Calculator: Pavers, Paver Base, Sand and Edging
- Wood Privacy Fence Calculator: Posts, Rails, Pickets and Concrete
- Retaining Wall Block Calculator: Blocks, Caps, Gravel and Drainage