Trade Calculator App

CalcRig

The field calculator for every trade. 16+ calculators across electrical, HVAC, plumbing, and construction — all code-referenced, all free.

iOS • Free

The Problem

Trade calculator apps are fragmented. One app for wire sizing, another for duct sizing, a code book to verify either. The free alternatives are shallow — no code references, no formula transparency, results you can't cite to an inspector.

4 Trades, 16+ Calculators

Everything a multi-trade professional needs in one app.

Electrical

  • Wire Sizing (NEC 310.15)
  • Voltage Drop
  • Conduit Fill
  • Load Calculator
  • AWG Reference

HVAC

  • Duct Sizing (ASHRAE)
  • Heat Load (Manual J)
  • BTU Calculator
  • CFM Calculator
  • Refrigerant Charge

Plumbing

  • Pipe Sizing (UPC/IRC)
  • GPM Calculator
  • Water Pressure
  • Fixture Units

Construction

  • Concrete Volume
  • Drywall Estimate
  • Roofing Calculator
  • Framing Calculator
  • Paint Coverage

How We Built It

Architecture decisions that made 16+ calculators maintainable.

Code-Referenced Results

Every calculation shows the formula used and the code standard behind it — NEC, ASHRAE, UPC, or IRC. Results you can cite to an inspector.

Pure Calculation Engine

All calculation logic separated from UI in pure TypeScript functions. Testable, reliable, consistent across all 16+ calculators.

Built for the Field

Dark UI with high-contrast text and large tap targets. Designed for outdoor use, sunlight legibility, and gloved-hand interaction.

Calculation History

Full parameter persistence — restore any past calculation, modify inputs, and recalculate. Not just a log of numbers.

Tech Stack

Mobile App

React Native 0.83

Cross-platform native app

Expo SDK 55

Managed native workflow

TypeScript

Type-safe calculations

Expo Router

NativeTabs per trade

Styling & State

NativeWind v5

Tailwind v4 in RN

op-sqlite

Local SQLite database

Drizzle ORM

Type-safe history schema

MMKV

Fast preferences storage

Backend & Build

Hono + Drizzle

REST API on Postgres

Better-Auth

Session-based auth

Orval

Generated React Query client

EAS Build

iOS / Android distribution

16+

Calculators

4

Trades Covered

Free

All Calculators

100%

Code-Referenced

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