PopularSquare FootageStairsStair StringerRoofingRoof PitchVoltage DropWire SizeConcreteConcrete Bags
Field-ready calculators for the US trades
Measure twice.
Quote once.
Free online construction and electrical calculators for contractors, estimators and serious DIYers. Calculate square footage, stairs, roofing, concrete, wire size and voltage drop in familiar US units.
✓ No signup✓ Mobile first✓ On-device calculations
MEASUREMENT
US UNITSSquare Footage
YOUR ESTIMATE
240 sq ft26.7 sq yd20 ft × 12 ft · Geometric area before waste
✓ Instant calculation on your device · Verify code-sensitive work locally
Beyond the calculator
Know what to measure before you estimate.
Original field guides connect each result to a repeatable measurement process, a worked example and the checks that still belong outside the calculator.
01
Explore all 39 articles →How to Measure Square Footage Without Guessing
A practical room-measurement method for rectangles, L-shaped spaces, walls and flooring estimates, with a complete worked example.
4 minute read · Read article →02Concrete Slab Estimate: From Dimensions to an Order Check
Calculate slab volume, compare ready-mix yards with bag quantities and avoid the measurement errors that commonly change a concrete order.
4 minute read · Read article →03Roof Measurement Checklist Before You Estimate Materials
Document roof planes, pitch, overhangs and complexity before calculating roof area, roofing squares, waste or material cost.
4 minute read · Read article →04Voltage Drop vs. Wire Size: Two Checks, Not One Answer
Understand what voltage-drop and wire-size calculators can estimate, what inputs change the result and which safety checks remain outside the calculation.
4 minute read · Read article →Electrical calculator collection
Plan wire runs with the right numbers in view.
Use the wire size calculator to estimate a minimum AWG by voltage drop, then check the expected voltage loss for the selected conductor. Both tools support copper, aluminum, DC, single-phase and balanced three-phase inputs.
Free construction calculators
The right tool,
right at the top.
No digging through menus. Every construction and electrical calculator opens with sensible US defaults, clear inputs and a result you can use immediately.
01FAST AREA ESTIMATE
MEASUREMENT
Square Footage Calculator
Calculate the square footage of a room from feet and inches, with square yards included.Open calculator ↗
02STEP & RUN PLAN
CARPENTRY
Stair Calculator
Calculate stair rise and run, riser count, tread count, riser height and angle.Open calculator ↗
03JOB-SITE READY
CARPENTRY
Stair Stringer Calculator
Calculate stair stringer length, stock-board length, angle and estimated stringer count.Open calculator ↗
04MATERIAL ESTIMATE
HIGH-VALUE ESTIMATE
Roofing Calculator
Calculate roof area, roofing squares, shingle waste and material cost from pitch.Open calculator ↗
05ANGLE & RAFTER
ROOFING
Roof Pitch Calculator
Calculate roof pitch in degrees, slope multiplier and rafter length from rise per 12.Open calculator ↗
06LOAD VOLTAGE CHECK
ELECTRICAL
Voltage Drop Calculator
Calculate voltage drop, percent loss and load voltage for AC, DC and three-phase circuits.Open calculator ↗
07VOLTAGE-DROP SIZING
ELECTRICAL
Wire Size Calculator
Estimate a copper or aluminum AWG candidate from voltage, current, one-way distance and a voltage-drop target.Open calculator ↗
08SLAB VOLUME
CONSTRUCTION
Concrete Calculator
Calculate concrete volume in cubic yards and 80 lb bags for slabs, pads and rectangular footings.Open calculator ↗
0940–80 LB OPTIONS
CONSTRUCTION
Concrete Bag Calculator
Calculate how many 40, 50, 60 or 80 lb bags of concrete a rectangular project needs.Open calculator ↗
10NEW CALCULATOR
Concrete & Masonry
Concrete Block Calculator
Estimate nominal concrete masonry unit count from wall dimensions, openings, block face size and waste allowance.Open calculator ↗
11NEW CALCULATOR
Roofing
Metal Roofing Calculator
Estimate panel count and sloped panel length for one rectangular metal-roof plane from pitch and effective coverage width.Open calculator ↗
12NEW CALCULATOR
Concrete & Masonry
Concrete Footing Calculator
Calculate concrete volume in cubic feet and cubic yards for continuous rectangular footings using total length, width, depth, and waste.Open calculator ↗
13NEW CALCULATOR
Concrete & Masonry
Post Hole Concrete Calculator
Estimate concrete volume and 40 to 80 lb bag counts for round post holes in feet and inches, automatically subtracting buried post displacement.Open calculator ↗
14NEW CALCULATOR
Carpentry & Framing
Board Foot Calculator
Calculate total and per-piece board feet from nominal or actual lumber thickness, width, length, and piece count for US timber estimates.Open calculator ↗
15NEW CALCULATOR
Electrical
Watts to Amps Calculator
Convert real electrical power in watts to estimated current in amps across DC, single-phase, and balanced three-phase circuits.Open calculator ↗
16NEW CALCULATOR
Electrical
Amps to Watts Calculator
Convert electrical current in amps to real power in watts using circuit voltage, power factor, and DC, single-phase, or three-phase mode.Open calculator ↗
17NEW CALCULATOR
Electrical
kVA to Amps Calculator
Convert apparent power in kilovolt-amperes (kVA) to load current in amps for single-phase and balanced three-phase US electrical systems.Open calculator ↗
18NEW CALCULATOR
Concrete & Masonry
Concrete Wall Calculator
Estimate poured concrete wall volume in cubic yards and cubic feet while subtracting window and door openings and adding order allowance.Open calculator ↗
19NEW CALCULATOR
Concrete & Masonry
Concrete Column Calculator
Calculate cubic feet and cubic yards for identical round concrete columns or Sonotube piers using diameter, height, count, and allowance.Open calculator ↗
20NEW CALCULATOR
Concrete & Masonry
Concrete Weight Calculator
Convert concrete volume in cubic yards to estimated weight in pounds and US short tons using your chosen concrete unit density.Open calculator ↗
21NEW CALCULATOR
Carpentry & Framing
Plywood Sheet Calculator
Estimate whole 4×8 plywood or OSB subfloor and sheathing sheet counts from measured surface area, sheet dimensions, and cutting waste.Open calculator ↗
22NEW CALCULATOR
Roofing
Roof Shingle Calculator
Convert measured sloped roof area into whole shingle bundles and roofing squares using product bundle coverage and waste allowance.Open calculator ↗
23NEW CALCULATOR
Roofing
Roof Underlayment Calculator
Estimate synthetic or felt roofing underlayment roll counts from measured sloped roof area, lap allowance, and installed roll coverage.Open calculator ↗
24NEW CALCULATOR
Roofing
Ridge Cap Calculator
Estimate hip and ridge cap shingle bundles from combined linear ridge and hip footage, cutting waste, and product coverage per bundle.Open calculator ↗
25NEW CALCULATOR
Carpentry & Framing
Rafter Length Calculator
Estimate common rafter slope length and framing stock length from building span, ridge thickness, roof pitch, and horizontal overhang.Open calculator ↗
26NEW CALCULATOR
Concrete & Masonry
Gravel Calculator
Calculate gravel, crushed stone, or pea gravel needed in tons and cubic yards from project length, width, depth, and waste allowance.Open calculator ↗
27NEW CALCULATOR
Electrical
Conduit Fill Calculator
Calculate NEC conduit fill percentage, allowable wire count, and raceway capacity for EMT and Schedule 40 PVC with THHN copper conductors.Open calculator ↗
28NEW CALCULATOR
Carpentry & Framing
Drywall Calculator
Calculate 4x8 and 4x12 drywall sheet counts, joint compound, screws, and tape from room dimensions, ceiling height, and openings.Open calculator ↗
29NEW CALCULATOR
Carpentry & Framing
Wall Stud Calculator
Calculate 2x4 and 2x6 wall studs, 16 or 24 inch on-center spacing, corner posts, and top/bottom plate lumber with waste allowance.Open calculator ↗
30NEW CALCULATOR
Concrete & Masonry
Rebar Calculator
Calculate rebar grid lines, lap splices, total linear feet, 20 ft stock bar counts, and steel weight for concrete slabs.Open calculator ↗
31NEW CALCULATOR
Concrete & Masonry
Paver Calculator
Calculate patio pavers, 4-inch gravel base, bedding sand, edge restraints, and cutting waste for patios and walkways.Open calculator ↗
32NEW CALCULATOR
Measurement
Tile Calculator
Calculate floor and wall tile square footage, full retail boxes to purchase, cutting waste allowance, and grout bag requirements.Open calculator ↗
33NEW CALCULATOR
Measurement
Paint Calculator
Calculate interior wall and ceiling paint, doors and window deductions, coats, gallons and quarts to buy, and primer.Open calculator ↗
34NEW CALCULATOR
Carpentry & Framing
Fence Calculator
Calculate fence posts, 2x4 horizontal rails, dog-ear pickets, post-hole concrete bags, and gate hardware for privacy and picket fences.Open calculator ↗
35NEW CALCULATOR
Concrete & Masonry
Mulch Calculator
Calculate landscaping mulch, topsoil, and garden bed depth in cubic yards, cubic feet, 2 cu ft and 3 cu ft retail bags, and bulk truckloads.Open calculator ↗
Built for real work
Answers that make sense on a jobsite.
Generic calculator sites make you translate units and hunt for the useful number. Calc for Trades puts the estimate, material quantity and practical next step together.
- 01
Enter familiar measurements
Use feet, inches, AWG and US construction units without manual conversions.
- 02
See the result instantly
Every field updates the answer—no reload, account or email required.
- 03
Plan with useful quantities
Get squares, bags, stair geometry and voltage-loss guidance, not just raw math.
FIELD NOTEBuilt as a fast reference—not a replacement for plans, codes or a licensed professional.
Clear by design
Useful first.
Responsible always.
We show formulas, units and assumptions next to each result. Electrical and structural work should always be checked against the applicable US code, manufacturer instructions and local requirements.
Common questions
Before you calculate.
Are these calculators free?+
Yes. The current web calculators work without an account or payment.
Can I use Calc for Trades on my phone?+
Yes. Inputs, buttons and results are designed for one-handed use on a jobsite.
Are results code-compliant?+
They are estimates based on stated formulas. Verify electrical, structural and permit work against the current local code and a qualified professional.
READY FOR THE NEXT MEASUREMENT?