Guides
Practical, worked-through answers to common engineering questions — each paired with a free calculator.
How to Size a Wire for a Subpanel
A step-by-step guide to sizing feeder conductors for a subpanel, covering load, ampacity and voltage drop.
How Many Amps Can 12 Gauge Wire Handle?
12 AWG copper wire ampacity explained, with the standard answer, the exceptions, and how temperature and bundling change it.
How to Calculate BTU for a Room (Cooling Load Basics)
Learn the quick rule-of-thumb method for estimating air conditioner size, and when you need a full Manual J calculation instead.
NEC Conduit Fill Rules Explained
How conduit fill percentage limits work, why they exist, and how to calculate them for any conductor and conduit combination.
Voltage Drop in 12V Systems: RV, Van & Solar Wiring Guide
Why voltage drop matters so much more in 12V DC systems, and how to size wire correctly for RVs, van conversions and off-grid solar.
How Much Rebar Do I Need for a Slab?
A practical guide to estimating rebar quantity and weight for a concrete slab, from spacing decisions to lap splice allowances.