Trade Math Study Guide
Updated September 26, 2025
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Math shows up everywhere in the trades—from measuring to layout to code compliance. This guide focuses on the essentials you’ll actually use on the job and in aptitude tests.
Fractions and Decimals
- Convert by multiplying/dividing by powers of 10; reduce to lowest terms
- Common conversions: 1/8 = 0.125, 1/16 = 0.0625, 3/4 = 0.75
Ratios and Proportions
- Cross‑multiply: a/b = c/d → ad = bc
Unit Conversions
- Inches ↔ feet ↔ yards; ounces ↔ pounds; PSI ↔ inches of water column (trade‑specific)
- Use dimensional analysis; write units and cancel
Geometry
- Rectangle area A = L×W; Triangle A = (b×h)/2
- Circle: C = 2πr, A = πr²; Pipe circumference ≈ 3.1416×D
Right‑Triangle Trig (layout and electrical)
- SOH‑CAH‑TOA; angle = arctan(opposite/adjacent)
- Pythagorean theorem: a² + b² = c²
Percent and Tolerances
- Percent change = (new−old)/old × 100%
- Tolerance windows for diameters, gaps, and clearances
Practice Plan (6 Hours)
- 2h: Fractions/decimals/ratios — 60 problems
- 2h: Unit conversions + geometry — 40 problems
- 2h: Right triangles + percent/tolerance — 40 problems
- Use the same calculator allowed on your test/job
- Tape measure, square, level; learn reading to 1/16” (or metric equivalent)
Apply It on the Job
- Electrical: voltage drop, conduit bends, load calculations
- HVAC: superheat/subcooling, airflow, psychrometrics basics
- Plumbing: pipe cut length, slope, flow considerations
- Welding: layout angles, material takeoff, distortion allowances
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