Construction calculators that cite the code

Most trade calculators hand you a number and no reason to believe it. These name the standard, print the table, show the work, and say so plainly when no table exists.

Concrete

Volume, bags, block and rebar, with the strength and air-entrainment requirements the code attaches to the pour.

• Brick CalculatorJoint and tie requirements quoted from IRC R606.3.1 and R606.13.2
• Concrete Block CalculatorNominal module from CMHA CMU-TEC-001-23, mortar types from ASTM C270
• Concrete CalculatorBag yields from the data sheets, strength from IRC Table R402.2
• Concrete Driveway CalculatorThe garage floor row of Table R402.2 is the honest benchmark
• Concrete Finish CalculatorPublished finish rates, carried forward over the life of the floor
• Concrete Footing CalculatorPier and column pads sized the way R403.1.1 sizes them
• Concrete Patio CalculatorThe only code figure that touches a patio is Table R402.2
• Concrete Sidewalk and Curb CalculatorA curb is a cross-section, not a thickness
• Concrete Slab CalculatorIRC Section R506 in full: base course, vapor retarder and where the steel sits
• Concrete Stairs CalculatorVolume from the stepped section, not from a length
• Foundation CalculatorAll 648 cells of IRC Tables R403.1(1), (2) and (3)
• Mortar CalculatorVolume from geometry, checked against the bag's own two claims
• Rebar CalculatorBar table from TxDOT Item 440, checked against its own geometry
• Retaining Wall CalculatorIRC R404.4, both thresholds, quoted
• Stone Veneer CalculatorIRC R703.12, which points straight at the stucco barrier clause
• Stucco CalculatorTable R702.1(1) thicknesses and the R703.7.5 curing schedule

Decking

Decks under IRC R507 and R312, fences where a published standard exists and where it does not, and the patio and surface takeoffs.

• Chain Link Fence CalculatorPost spacing and footing depth from the CLFMI product manual
• Composite Decking CalculatorSpacing read from each manufacturer's own guide. The IRC sets none.
• Deck Construction Cost EstimatorQuantities from IRC R507.6, R507.5(1) and AWC DCA 6 Table 4
• Deck Fastener CalculatorIRC R317.3.1 · connectors ASTM A653 G185 · ASTM A153
• Deck Footing CalculatorAWC DCA 6 Table 4 · footing depth per IRC R403
• Deck Load CalculatorLive load is an input, because it is not 40 psf everywhere
• Deck Lumber CalculatorActual lumber dimensions · gap per AWC and manufacturer guidance
• Deck Materials CalculatorIRC R507.5(1), R507.6, R312, R311.7 · AWC DCA 6 Tables 4 and C4A
• Deck Post CalculatorAWC DCA 6-2015 Table 4 · 4x4 heights from Table C4A
• Deck Railing CalculatorIRC R312 · guard load Table R301.5
• Deck Ramp CalculatorIRC R311.8 slope and landings, quoted with the edition read
• Deck Size CalculatorArea and perimeter, plus the IRC R312.1.1 guard trigger
• Deck Stain CalculatorCounts board edges, balusters and stairs. Coverage from the data sheets.
• Flagstone Patio CalculatorCoverage per ton from a supplier's own sheet, published as a range
• Gazebo Size and Cost CalculatorRegular polygon geometry; prices from HomeAdvisor's June 2026 gazebo guide
• Patio Cost CalculatorHomeAdvisor's patio guide by material, checked against its own flagstone guide
• Paver Patio CalculatorCounts the base and the spoil, not just the pavers
• Pergola and Patio Cover CalculatorIRC Appendix AH: 10 psf live load, 12 ft high, outdoor living only
• Privacy Fence CalculatorPost embedment: one-third rule · frost depth per local adoption
• Privacy Fence Cost CalculatorTakeoff from post embedment and picket layout · prices are cited, not ours
• Sod CalculatorPallet coverage is your producer's number, not a standard
• Split Rail Fence CalculatorArithmetic from your rail length. There is no published standard here
• Vinyl Fence CalculatorPost spacing from the Bufftech WindZone table, not a rule of thumb
• Wire and Farm Fence CalculatorBarb spacing from ASTM F1665. Post spacing is yours, and this says why

Drywall

Board, fasteners and tape under IRC Table R702.3.5, with the pairing of thickness to framing spacing that decides what you may use.

• Crown Molding CalculatorChecked against 240 published values from Starrett's own table
• Drywall CalculatorIRC Table R702.3.5 in full, including the garage ceiling row
• Plaster CalculatorIRC Tables R702.1(1) and R702.1(2), gypsum plaster
• Trim and Casing CalculatorIRC R311.2 measures the egress door from the stop

Electrical

Voltage drop from a public-domain government wire table, with the constant derived and the code tables that could not be obtained named as missing.

• Conduit Fill ChartIRC Tables E3904.6(1) to (10), the residential reprint of NEC Annex C
• Conduit and Box Fill CalculatorIRC Tables E3904.6(1) to (10) and E3905.12, the NEC's Annex C and 314.16 for dwellings
• Electrical Work Cost EstimatorHomeAdvisor's electrician and outlet guides, device prices separated from the job
• Recessed Lighting Cost CalculatorHomeAdvisor's recessed and under-cabinet lighting guides, with the labor arithmetic checked
• Residential Electrical Load CalculatorIRC Table E3602.2 for the service, Table E3704.2(1) for a feeder
• Solar Panel CalculatorEIA estimated small-scale solar generation and capacity, by state
• Transformer Sizing CalculatorDOE 10 CFR 431.196 ratings and minimum efficiency
• Voltage Drop CalculatorConductor table from NBS Circular 31, a public-domain NIST publication
• Watt and Electricity Cost CalculatorConversions from NIST SP 811, rates from EIA Table 5.6.A
• Wire Ampacity ChartIRC Table E3705.1, the residential reprint of NEC Table 310.16
• Wire Size CalculatorIRC Chapter 37 ampacity tables, the NEC's Table 310.16 reproduced for dwellings

Estimating

How a construction price is actually built up, and why a cost per square foot means nothing until you know what it was divided by.

• Cost Per Square Foot CalculatorA ratio with an undefined denominator, and the perimeter it hides
• Countertop and Cabinet Cost CalculatorHomeAdvisor's countertop and cabinet guides, with the countertop guide's two sets of figures side by side

Flooring

Tile and grout quantities computed from the geometry behind the manufacturers' coverage charts, so they work for sizes no chart lists.

• Baseboard and Trim CalculatorIRC R302.9.1 names baseboard once, to exempt it
• Carpet CalculatorCRI 105 sections 5.1 and 5.2, quoted in full
• Epoxy Floor CalculatorSubstrate limits from a manufacturer's own data sheet
• Flooring CalculatorQuantities from manufacturer layout rules, prices quoted and dated
• Hardwood Flooring CalculatorLayout rules quoted from Bruce document 210049
• Laminate Flooring CalculatorLayout rules quoted from Pergo Installation Guide, Version 07.2026
• Tile CalculatorGrout coverage derived from the geometry a manufacturer's chart is made of

Framing

Walls, sheathing and lumber quantities, with the stud and span-rating tables printed in full and the cells that say no called out.

• 3-4-5 Rule CalculatorFM 5-426 squaring methods, with the tape error worked out
• Board Foot CalculatorA board foot is nominal volume. A third of it is not there
• Nail Size ChartUSDA Wood Handbook Tables 8-1 to 8-3, checked against IRC Table R602.3(1)
• Screw Size ChartUSDA Wood Handbook Tables 8-9 and 8-11, NBS Handbook H28 Table 2.7
• Sheathing and Subfloor CalculatorIRC Table R503.2.1.1(1) and the APA span rating: two numbers, one sheet
• Shed Framing CalculatorFraming arithmetic, and the size threshold that is not framing at all
• Wall Framing CalculatorIRC Table R602.3(5). A 2x4 under two floors is a dash, not a spacing
• Wrench Size ChartASME B18.2.1 and B18.2.2 as published, RCSC Table C-2.1, ISO 4014 and DIN 931

HVAC

Heating and cooling loads computed from the envelope, with everything a full Manual J adds named rather than left silent.

• AC Tonnage Calculator12,000 Btu/h per ton by definition. DOE on why square feet per ton oversizes
• BTU CalculatorQ = U x A x dT over the whole envelope. The DOE on why rules of thumb oversize
• Duct Size CalculatorDarcy-Weisbach with McGill AirFlow's friction factor and Table A.21 roughness; IRC M1601.1
• Ductless Mini Split Cost CalculatorHomeAdvisor's ductless heat pump guide, its zone table set against its own per zone figure
• Exhaust Fan CFM Calculator2021 IRC M1505.4.3 and M1505.4.4
• Furnace Size and Cost CalculatorIRC M1401.3 against the 30 to 60 BTU per square foot rule
• Heat Load Calculator: Heating Load by CountyENERGY STAR county design temperatures, IRC N1102.4.1.2 air leakage, conduction plus infiltration
• Refrigerant Pressure Temperature ChartHudson Technologies PT charts, checked against the Bonneville Power Administration R-410A chart

Insulation

The prescriptive minimum for your zone in every code edition still enforced, and the whole-assembly R-value your build-up actually delivers.

• Attic Insulation CalculatorEave geometry, and the R807.1 access opening
• Blown-In Insulation CalculatorCoverage chart required on the bag by 16 CFR 460.12(b)(2)
• Insulation CalculatorTwo federal rules name R-19 batts, and nothing else
• R-Value CalculatorIECC and IRC minimums, all four editions, from US DOE
• Radiant Barrier CalculatorRoof deck area from the attic plan and pitch; prices from HomeAdvisor's June 2026 guide
• Spray Foam Insulation CalculatorIRC R316 barriers, and 16 CFR 460.13 at 3 1/2 inches

Paint

Interior and exterior quantities from published coverage rates, with the waste allowance shown as a field rather than buried in a constant.

• Exterior Paint CalculatorGables counted as half base times rise. Coverage from Sherwin-Williams data sheets
• Paint CalculatorCoverage from Sherwin-Williams data sheets, checked against 1604 / wet mils

Plumbing

Septic sizing and onsite wastewater from state standards that are free to read, in a trade where the model codes are not.

• Drain Slope CalculatorIPC Table 704.1 against UPC 708.1, and they disagree at 3 inches
• Gas Pipe Sizing CalculatorFuel Gas Code tables 402.4(2) and 402.4(28), checked against their own equation
• Pipe Pressure Drop CalculatorCDA Copper Tube Handbook, Tables 14.2, 14.6 and 14.7
• Pipe Size ChartCDA Copper Tube Handbook Tables 14.2a to 14.2c, and IPC Table E202.1 for plastic
• Pipe and Conduit Offset CalculatorThe triangle, against the bending table a manufacturer prints
• Plumbing Cost EstimatorHomeAdvisor's plumber and repipe guides, with the places they disagree
• Septic Tank and Drainfield CalculatorKansas KDHE Bulletin 4-2, a state regulator's own standard
• Sewer Line Size and Replacement CalculatorIPC Tables 709.1 and 710.1(1), and the size limits in Sections 716 and 717
• Water Heater Size CalculatorGeorgia Table 506, the federal first hour rating rule and A. O. Smith's sizing guide
• Water Pipe Size CalculatorIPC Appendix E sizing, and the tables in it that disagree with each other

Roofing

Roof areas, squares and bundles from footprint and pitch, with the IRC Chapter 9 requirements that change with the same pitch.

• Flat Roof CalculatorEvery low-slope minimum in R905, and they are design slopes
• Gutter CalculatorFlow from unit arithmetic, because the IRC does not size gutters
• Metal Roof CalculatorR905.10.2, three minimum slopes for the same metal
• Roof Flashing CalculatorIRC R905.2.8, quoted, including the drip edge nobody reads
• Roof Pitch CalculatorTrigonometry, plus the IRC R905 thresholds the same pitch trips
• Roof Replacement Cost CalculatorAreas from the slope factor, prices quoted from a dated third party
• Roof Tile CalculatorR905.3.2 and R905.3.6, and the weight nobody checks
• Roof Underlayment CalculatorR905.1.1, the doubling bands, and R905.1.2
• Roof Ventilation CalculatorIRC R806.2, both conditions and the band
• Roofing CalculatorSlope factor computed, not tabulated. IRC R905 requirements by pitch

Siding

Siding by exposure rather than area, plus the water-resistive barrier R703.2 requires underneath and both of its laps.

• Fiber Cement Siding CalculatorR703.2 barrier laps and the R703.3.2 wind limits
• Siding CalculatorIRC R703.2 water-resistive barrier, with both of its lap dimensions
• Soffit and Fascia CalculatorIRC R703.3.1.1 and R703.3.1.2, two materials, two rules
• Vinyl Siding CalculatorR703.11 fasteners and the R703.3.2 wind limits
• Wood Siding CalculatorR703.2 barrier laps and the R703.3.2 wind limits

Site

Volumes in cubic yards with a compaction allowance, and an honest account of why the tonnage needs a density only your supplier has.

• Asphalt Sealer CalculatorCoverage read from four manufacturer data sheets
• Cubic Yard and Truck Load CalculatorAxle and gross weight limits, 23 CFR 658.17
• Excavation and Grading CalculatorMaximum allowable slope, 29 CFR 1926 Subpart P Appendix B
• Gravel CalculatorSolid rock density derived from WSDOT's own riprap equivalences
• Inground Pool Cost CalculatorHomeAdvisor's inground pool guide, its size table checked against its own per square foot range
• Mulch CalculatorMaximum depth by material texture, Clemson HGIC 1604
• Sand CalculatorFour WSDOT fine aggregate gradings, and the sieve that separates them
• Topsoil CalculatorWSDOT 9-14.2, where two of three topsoil types are defined by provenance

Structural

Members whose size is a table lookup rather than a calculation, plus the three where no table exists and the page says so.

• Beam Load and Deflection CalculatorIRC Table R301.7 deflection limits, and the honest answer on sizing
• Deck Beam CalculatorIRC Table R507.5(1) · NDS design values
• Deck Ledger CalculatorIRC Table R507.9.1.3(1), all 84 cells, read from the code
• Gauge Size Chart15 U.S.C. 206 (1893), NBS Circulars 391 and 31, IRC 2021
• Header and Girder Size CalculatorIRC Table R602.7(1), read cell by cell from the code
• Joist CalculatorIRC Table R507.6 · cantilever rule R507.6.1
• Occupant Load CalculatorIBC Table 1004.5, every row, with gross and net marked
• Rafter CalculatorIRC R802.4.1: the span is the horizontal projection, not the rafter
• Roof Truss CalculatorIRC R802.10 and ANSI/TPI 1: a truss is a sealed engineered design
• Spiral Staircase Calculator2015 IRC R311.7.10.1 spiral stairways; prices from HomeAdvisor's June 2026 guide
• Stair Construction CalculatorIRC R311.7 · riser R311.7.5.1 · tread R311.7.5.2
• Steel I-Beam CalculatorExact geometry for an I-shape. The IRC has no steel beam table at all
• Steel Weight Calculator490 lb per cu ft carbon steel (AASHTO via FHWA); stainless and aluminum from mill datasheets
• Structural Load CalculatorIRC Table R301.5, and the rule that snow and live load are not added

Windows and doors

Windows and doors measured the way the code measures them, net clear opening rather than glass size, with sourced prices alongside.

• Door Rough Opening CalculatorMasonite and JELD-WEN installation instructions, read side by side
• Garage Door Size and Headroom CalculatorClopay and Wayne Dalton installation manuals, compared figure by figure
• Window Replacement CalculatorIRC R310 net clear opening, measured the way the code measures it

There is no shortage of construction calculators. Type almost any sizing question into a search engine and you will get a dozen results, most of them a form and a result and nothing else: no table, no code section, no statement of what load or service condition the number assumes. That last omission is the one that matters, because a span figure without its assumptions is not an answer. The same 2×10 spans one distance as a deck joist and a noticeably longer one as an interior floor joist, and a tool that does not say which it calculated has hidden the only decision in the problem.

Some of them are simply wrong. While building the deck beam page here, two of the highest-ranking deck calculators on the web disagreed with each other and with the actual values in IRC Table R507.5(1). The table itself shows how easy the error is: a 2-ply 2x10 carrying 6 ft joists spans 10 ft 4 in in southern pine and 8 ft 4 in in Douglas fir-larch. Read the wrong column and you are 24% over, on a member that holds people several feet off the ground.

What is different here

Every page names its source and prints the table it reads from, in full, as real text you can search and copy. The worked example shows the arithmetic. The assumptions (live load, dead load, deflection limit, grade, wet or dry service)are stated rather than buried. And where a table stops applying, the page says so and stops, instead of quietly extrapolating past the edge of its own data.

Six checks run automatically on every build. The visible table and the calculator's internal lookup come from a single source, so they cannot drift apart. Every figure quoted in the prose is executed against that data, so a paragraph that disagrees with the table beneath it does not publish. Every diagram is run against the results its page actually produces, because a drawing that has silently stopped reacting looks identical to one that works. Outbound citations are fetched, because a page that says to check a standard and links to a 404 is worse than one that never linked out. The link graph is walked so nothing is orphaned. And a section page with no authored copy is refused outright, because a hub that is only a list of links is a doorway page.

Where a value could not be verified against the source itself, the page does not exist yet. Several planned calculators are on hold for exactly that reason, and a few that were built carry a cell marked not published rather than a figure borrowed from a neighbor.

Sometimes there is no table, and that is the answer

The most useful thing several of these pages do is refuse. A roof truss cannot be sized from a table by anybody: the code hands it to a sealed engineered design and requires the drawing to be approved before installation, so a calculator that prints a member size is producing a number nobody will sign. The IRC has no steel beam table for dwellings at all. It sets no joist spacing for composite decking either, deferring entirely to the board's own manufacturer, whose published figures run from 8 in to 24 in.

The same applies at the edges of tables that do exist. The ledger connection table stops at an 18 ft joist span and its own footnote forbids reading past it. The stud table prints a dash where a wall is not permitted, which is not a tighter spacing you can reach by adding studs. Those pages say so and stop, which is the part a form and a result cannot do.

And no price here is ours. Where a page needs one to be useful it quotes somebody else's, with a byline and the date it was read, and says whose it is.

Who this is for

Pros who want the number and the citation and nothing in between, and homeowners who want the number plus enough plain explanation to trust it. Both should find the page readable without scrolling past an essay to reach the tool.

Nothing is sold here. No accounts, no sign-up, no quote forms. The calculators run entirely in your browser and nothing you type leaves it. The method, the full source list, and the traps found along the way are in Sources & Method.