FieldDojo: Trade Calculators

notchip's lab

In-app purchases

About this app

FieldDojo puts the calculators trade pros actually use in one fast, offline app. Built for electricians, plumbers, HVAC technicians, framers, concrete crews, and general contractors who need answers on the job — not a paywall and a sign-up form.
Every calculator runs on-device. No account required. Switch between imperial and metric with one tap. Save every result to history, then export as PDF or plain text for estimates, permits, or client records.

▸ ELECTRICAL
• Wire gauge recommendation by amperage
• Voltage drop (and reverse: wire size for max drop)
• Conduit fill per NEC tables
• Residential load calculation (NEC 220)

▸ PLUMBING
• Pipe sizing by fixture units
• Flow rate (Hazen-Williams)
• Drainage slope and pitch
• Water heater sizing

▸ HVAC
• Manual J heat load
• Duct sizing
• Refrigerant charge
• Air changes per hour (ACH)

▸ CONSTRUCTION
• Concrete volume (slabs, footings, columns)
• Board feet for lumber takeoffs
• Stud count for framing
• Drywall sheet count
• Roofing squares
• Paint coverage

▸ WHY CALCJAW
• 100% offline — works in basements, attics, crawl spaces, no signal needed
• Imperial and metric, switch instantly
• Calculation history saved automatically
• PDF and text export for documentation
• No ads, no popups, no tracking inside calculations
• Clean interface designed for gloved hands and bright sunlight

▸ FOR PROS, BY PROS
FieldDojo is not a homeowner toy. The formulas reference NEC, Manual J, and standard fixtures used in the field. Each calculator shows the formula so you can verify, document, or teach an apprentice.

▸ NOT A SUBSTITUTE FOR CODE
FieldDojo is a calculation aid. Always verify against your local jurisdiction's adopted code, manufacturer specifications, and licensed engineering review where required. FieldDojo does not provide engineering, legal, or code-compliance advice.


Support: [e-mail]
Privacy: see in-app Settings → Privacy Policy

What’s new

• FieldDojo Pro is now available on Android — cloud sync, branded PDF export, and unlimited history
• Export to CSV: project sheets, your projects list, and Quick Calc (free)
• PDFs show their work: inputs, code basis, and a signature block, with your company details in the header (Pro)
• New Company section in Settings
• Smoother, faster start after setup
• Fixes: email wrapping in Settings, project “not found” flash, CSV encoding in Excel