General Construction Calculators
Cross-trade field math, takeoffs, and estimating helpers.
Electrical
11 TOOLSNEC code checks and electrical design calculators.
- VDVoltage Drop CalculatorNEC Table 9 voltage drop with the 3% branch check.
- AMPWire Ampacity & Derating CalculatorDerated ampacity per NEC Table 310.15(B)(16).
- FILLConduit Fill CalculatorMixed-conductor fill vs. 53 / 31 / 40% limits.
- BOXBox Fill CalculatorNEC 314.16 volume vs. conductor & clamp counts.
- FLAMotor FLA CalculatorFLA from HP, voltage & phase per NEC tables.
- kVATransformer Sizing CalculatorkVA and amps, single- and three-phase.
- LOADService & Load CalculatorDwelling & commercial loads to size the service.
- BENDConduit Bending CalculatorOffset & saddle multipliers, shrink & marks.
- ΩOhm's Law & Power CalculatorVolts, amps, ohms & watts from any two values.
- GENGenerator Sizing CalculatorRunning & starting kW with motor inrush.
- LUXLighting Layout CalculatorFixture counts & a dimensioned room layout map.
Plumbing
7 TOOLSPipe sizing, flow, drainage, and capacity.
- VOLPipe Volume & Capacity CalculatorGallons per foot & total fill by pipe size.
- ¼"Drainage Pipe Slope CalculatorFall over a run and the minimum-grade check.
- PSIWater Pressure Loss CalculatorFriction loss through pipe & fittings at GPM.
- DFUFixture Unit CalculatorDFU / WSFU totals from fixture counts.
- SIZEPipe Sizing CalculatorDiameter from flow, length & allowable loss.
- TANKTank Volume CalculatorCylinder, rectangle & oval capacity in gallons.
- GPMGPM Flow Rate CalculatorGPM from pipe size & velocity — or the reverse.
HVAC & Mechanical
6 TOOLSAirflow, loads, duct sizing, and refrigeration.
- DUCTDuct Size CalculatorRound & rect sizes from CFM and friction rate.
- CFMCFM & Airflow CalculatorCFM from room volume and target air changes.
- BTUBTU & Heat Load CalculatorBTU/hr load from area, climate & construction.
- TONCooling Tonnage CalculatorBTU/hr to tons of cooling, and back.
- ESPStatic Pressure CalculatorTotal ESP from duct, coil & filter losses.
- REFRefrigerant Line Charge CalculatorAdded charge for line length past pre-charge.
Fire Alarm
7 TOOLSNFPA 72 battery, circuit, and notification math.
- BATTFire Alarm Battery CalculatorNFPA 72 standby battery sizing + submittal sheet.
- NACNAC Voltage Drop Calculator20.4 V NAC drop — EOL & point-to-point methods.
- CKTNAC Circuit Loading CalculatorPer-circuit & supply amp checks with headroom.
- CDStrobe Candela CalculatorNFPA 72 candela by room, corridor & sleeping area.
- 0.7SSmoke Detector Spacing CalculatorNFPA 72 spacing — 0.7S, beams, ACH & heat modes.
- 70VSpeaker Circuit Calculator25/70.7 V taps, amp loading, dB loss & audibility.
- SLCSLC Loading CalculatorLoop points, wire limits & isolators by panel.
Carpentry & Framing
6 TOOLSLumber, framing, stairs, rafters, and decking.
- BDFTBoard Foot CalculatorBoard feet & cost from nominal size and count.
- STUDStud & Framing CalculatorStuds, plates & lineal feet from wall length.
- STRStair CalculatorRiser, tread & stringer layout from total rise.
- RFTRRafter & Roof Pitch CalculatorRafter length & cuts from pitch and span.
- JOISTJoist Span CalculatorAllowable spans by species, size & spacing.
- DECKDecking CalculatorBoards, joists & fasteners from deck size.
Concrete & Masonry
6 TOOLSVolume, rebar, block, brick, and mortar takeoffs.
- CONCConcrete Volume CalculatorYards for slabs, footings & columns, with bags.
- REBRRebar Weight & Spacing CalculatorBar count, length & weight from grid spacing.
- CMUBlock / CMU CalculatorBlock count, courses & mortar for a wall.
- BRCKBrick CalculatorBrick count & mortar from wall area and size.
- MRTRMortar & Grout CalculatorBags of mortar or grout for block & cell fill.
- FOOTFooting CalculatorVolume & rebar for continuous and pad footings.
Earthwork & Site
6 TOOLSExcavation, cut & fill, trenching, and aggregate.
- EXCVExcavation Volume CalculatorBank yards from area & depth, with swell.
- C/FCut & Fill CalculatorNet import / export from average cut & fill.
- TRCHTrench Volume CalculatorSpoil, bedding & backfill for a trench run.
- AGGAggregate & Gravel TonnageTons of gravel, sand or base from area & depth.
- CMPTCompaction CalculatorLoose vs. compacted volume and lift counts.
- SWELSoil Swell & Shrink CalculatorBank, loose & compacted volume conversions.
Roofing & Exterior
6 TOOLSRoof area, pitch, shingles, panels, and gutters.
- AREARoof Area & Pitch CalculatorTrue area & squares from footprint and pitch.
- SHGLShingle & Bundle CalculatorBundles & squares, plus starter and ridge.
- PTCHRoof Pitch MultiplierPitch to angle, slope factor & multiplier.
- UNDRUnderlayment CalculatorRolls of felt or synthetic from area & overlap.
- PNLMetal Roofing Panel CalculatorPanels & lineal feet from roof and panel width.
- GUTRGutter & Downspout CalculatorGutter feet & downspouts from drainage area.
Drywall, Paint & Finishes
6 TOOLSDrywall, paint, tile, flooring, and insulation.
- DRYDrywall Sheet CalculatorSheets, screws & tape from wall & ceiling area.
- PNTPaint Coverage CalculatorGallons per coat from area and spread rate.
- MUDJoint Compound CalculatorMud boxes & tape footage by finish level.
- TILETile CalculatorTile count, thinset & grout from area and waste.
- FLRFlooring CalculatorBoxes & underlayment from room area and waste.
- RInsulation CalculatorBatts or blown bags from area and R-value.
General & Shared
7 TOOLSCross-trade field math, takeoffs, and estimating helpers.
- YD³Construction CalculatorConcrete yards, aggregate tons & unit conversions.
- FT²Square Footage CalculatorArea & perimeter with multi-room totals.
- 3·4·5Right-Angle (3-4-5) CalculatorDiagonals & hypotenuse to square up corners.
- %Slope & Grade Calculator% grade, ratio, degrees & rise/run conversions.
- %↑Markup & Margin CalculatorMarkup vs. margin & price to a target profit.
- HRSLabor & Crew Cost EstimatorBurdened crew cost per hour and per day.
- FUELEquipment Fuel Cost CalculatorFuel burn & cost by machine and run hours.
Market Data
3 TOOLSLive-ish prices and trends for the materials you buy.
ABOUT THESE TOOLS
Every trade leans on the same core field math: how many square feet, how many cubic yards, whether the corner is square, and what the work has to sell for. These calculators cover that shared layer — the combined construction calculator handles concrete volume, aggregate tonnage, and unit conversions in one place; the square footage and right-angle (3-4-5) tools handle layout and takeoff geometry; and the slope tool converts between percent grade, ratio, degrees, and rise over run for ramps, drainage, and site work.
The business-side tools matter just as much as the geometry. Markup and margin are not the same number, and pricing work with the wrong one silently gives away profit — the markup calculator flips between the two and back-solves the price for a target margin. The labor estimator builds a true burdened crew cost from wages, payroll burden, and crew mix, and the fuel calculator turns machine run hours into a daily operating cost. Together they cover the estimating math that shows up on every job, whatever the trade. Free, in the browser, no account required.