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Free calculators for your website

Updated Formulas shown

Give your readers an accurate, always-up-to-date calculator without writing code. Pick one, set the colors and width, and paste the snippet into your page.

How to embed one

  1. Open the calculator you want and scroll to "Embed this calculator on your site".
  2. Choose width, light or dark theme, accent color and compact mode — the live preview updates instantly.
  3. Copy the code and paste it into an HTML block. The widget adjusts its height automatically.

Measure (2)

  • Square Footage Calculator

    Free square footage calculator: add rectangles, L-shaped rooms, circles, triangles and trapezoids in ft, in or m.

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  • Board Foot Calculator

    Calculate board feet for a whole lumber list: thickness × width × length for each piece, nominal or actual sizes, price per boa…

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Framing & roofing (2)

  • Stair Calculator

    Stair calculator with a live diagram: number of steps, riser height, tread depth, total run, stringer length and angle, checked…

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  • Roof Pitch Calculator

    Convert rise and run or an angle into roof pitch (x/12), degrees, slope %, area multiplier and rafter length.

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Electrical (2)

  • Wire Size Calculator

    Find the right wire gauge (AWG) for any circuit: copper or aluminum, single or three phase, by amps, distance and voltage drop,…

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  • Voltage Drop Calculator

    Calculate voltage drop in volts and percent for copper or aluminum wire, single-phase, three-phase or DC, with NEC 3%/5% guidan…

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HVAC (1)

  • BTU Calculator

    Find the BTU you need to cool or heat a room from its size, ceiling height, insulation, sun, occupants and kitchen use.

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Landscaping & aggregates (16)

Gravel Calculator

Interior (11)

Area & volume conversions (7)

Concrete (6)

Decks, lumber & stairs (6)

  • Deck Calculator

    Free deck calculator: deck boards, joists at 16 in on center and screws for wood or composite decking.

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  • Deck Board Calculator

    Calculate deck boards for wood or composite decking by deck size, board width, gap and board length.

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  • Rafter Length Calculator

    Calculate common rafter length from building span, roof pitch, overhang and ridge thickness, with plumb and seat cut angles.

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  • Plywood Calculator

    Calculate 4×8 or 4×10 sheets of plywood or OSB for subfloors, walls and roofs, with waste and cost.

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  • Stud Calculator

    Calculate wall studs at 12, 16 or 24 inches on center, plus extras for corners and openings and plate lumber.

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  • Deck Stain Calculator

    Calculate gallons of deck stain from deck size, railing length, coats and coverage per gallon.

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Masonry & hardscape (6)

Electrical, HVAC & pools (6)

Roofing (5)

Project cost estimators (5)

Fencing (4)

Frequently asked questions

Is it really free to embed a calculator?

Yes. Every calculator on ProjectCalc is free to embed on any site, blog or intranet. We only ask that you keep the attribution link under the widget.

Does it work on WordPress, Squarespace or Wix?

Yes. Paste the snippet into a "Custom HTML" / embed block. If your platform strips the script tag, the iframe still works with a fixed height.

Will it slow down my page?

The iframe is lazy-loaded and the helper script is under 1 KB. Nothing loads until a visitor scrolls near it.

Can I match my brand colors?

Yes: pick light or dark, any accent color, a width, and a compact mode without the title. The widget resizes itself to fit its content.

Do you track my visitors?

No cookies and no personal data. Calculations run in the visitor's browser; we only count anonymous views.