Trade Calculators, Free to Use.
42 transparent planning estimates for electricians, HVAC techs, plumbers, and general contractors. Inspectable formulas, zero paywall.
Amp Conversions
Convert between watts and amps for single-phase and three-phase AC/DC circuits.
Ohm's Law
Solve for voltage, current, resistance, or power. Enter any two values.
Voltage Drop
Calculate voltage drop and percent drop for wire runs using NEC K-factor circular-mil method. Flags runs exceeding the NEC 210.19 recommended guideline and suggests the minimum passing conductor size.
Wire Ampacity
Find the derated ampacity of a conductor using NEC 310.16 base values with ambient temperature correction (NEC 310.15(B)(1)) and conductor-count adjustment (NEC 310.15(C)(1)). Enforces NEC 240.4(D) small-conductor caps and terminal temperature limits.
Conduit Fill
Check whether THHN conductors fit inside EMT, PVC Schedule 40, or RMC conduit using NEC Chapter 9 fill allowances (53%, 31%, 40%). Supports up to two conductor groups and nipple/sleeve mode (60%).
Conduit Bending
Calculate offset spacing, conduit shrink, and stub-up mark for hand-bent conduit at 10°, 22.5°, 30°, 45°, or 60°. Uses standard multipliers and bender take-up values with optional override.
Box Fill
Verify junction or device box volume against NEC 314.16 requirements. Counts current-carrying conductors, grounding conductors, internal clamps, and device yokes using Table 314.16(B) allowances.
BTU Rule of Thumb
Quick HVAC load estimate from square footage. Rule-of-thumb only — not a Manual J replacement.
CFM from ACH
Calculate required airflow (CFM) from air changes per hour and room volume.
Water Heater Cost Stack
Estimate total water heater replacement cost from equipment, labor, permit, materials, and disposal.
Concrete Slab
Cubic yards, bag count, and rebar quantity for a slab pour with explicit waste and lap splice inputs.
Concrete Volume
Cubic yards for slabs, footings, and cylinder columns.
Concrete Block Count
CMU block quantity from wall dimensions with explicit block size and mortar joint inputs.
Rebar Grid
Rebar piece count and lap splices for a concrete grid layout based on clear cover and spacing.
Retaining Wall Basic
Face unit count, capstones, and backfill volume for a simple retaining wall.
Stair Geometry
Rise, run, stringer length, and code checks from total floor-to-floor height.
Roof Pitch
Derive roof angle, pitch multiplier, and common rafter length from rise and run.
Roofing Area
Convert flat footprint to actual roof squares using pitch multiplier and waste.
Shingle Packaging
Calculate shingle bundles and felt rolls from roof area and packaging sizes.
Plywood / Sheet Goods
Sheet count for sheathing or subflooring from area and sheet dimensions.
Deck Surface
Decking rows, linear footage, and joist count from board width and spacing.
Lumber Pieces
Required lumber pieces from total linear footage or an individual cut list.
Board Foot
Board-foot volume of lumber from thickness, width, length, and quantity.
Drywall Sheets
Drywall sheet count from wall/ceiling dimensions and sheet size.
Tile Coverage
Tile count and box quantity using exact tile and grout joint dimensions.
Flooring Coverage
Box count for hardwood, vinyl, or laminate flooring from area and box coverage.
Carpet Coverage
Carpet square yards, seam count, and roll allowance from room dimensions and roll width.
Paint
Gallons needed from gross wall area, openings, coats, and coverage rate.
Siding Area
Net siding squares after subtracting openings, with waste factor.
Insulation Coverage
Insulation package count from area, coverage rate, and compression factor.
Paver Count
Paver quantity from exact paver dimensions and joint width.
Brick Count
Brick quantity from wall dimensions and exact brick and mortar joint sizes.
Mortar Volume
Mortar bag count from volume required and bag yield.
Gravel Volume
Gravel cubic yards and tonnage for rectangular or circular areas.
Mulch Volume
Mulch cubic yards and bag count from area and depth.
Soil Volume
Soil cubic feet, tons, and bag count from area and depth.
Asphalt Tonnage
Required asphalt weight in tons from area, thickness, density, and waste.
Cubic Yard Converter
Convert dimensions to cubic feet, cubic yards, and optional tonnage.
Pool Volume
Pool capacity in gallons for rectangular, circular, oval, or measured-area shapes.
Fence Layout
Post count, section count, and picket quantity from fence length and spacing.
All calculators provide planning estimates only. Results depend on your inputs and must be verified before use for any project, bid, permit, installation, or safety decision. Read the full Calculator Terms