How-to guides
Short, specific walkthroughs written from the field. Each one gives the method, the numbers, the code section it comes from, and the calculator that does the math. About five minutes each.
Pay & taxes
How Overtime Pay Is Calculated (and When You Are Owed It)
Time and a half on the regular rate after 40 hours, why a bonus week pays more, state daily rules and a worked example.
5 min read · updated Oct 7, 2026How to Read Your Paycheck: Gross Pay to Net Pay
Every line on a pay stub, the 2026 rates behind it, and why your take-home differs from an online estimate.
4 min read · updated Oct 7, 2026IRS Mileage Rate 2026: How to Claim the Mileage Deduction
The 2026 rates changed on July 1. Who can use the standard rate, what counts, the log you need and what it saves.
Electrical
How to Apply the NEC 3% Voltage Drop Rule
Why voltage drop matters, where 3% is only a recommendation, the K-factor formula with a worked example, and the fixes.
5 min read · updated Oct 7, 2026How to Do a Residential Panel Load Calculation
The NEC 220.82 optional method step by step, a 2,000 sq ft worked example that comes to 103 A, and when to use 220.40 or 220.83 instead.
5 min read · updated Oct 7, 2026How to Size Wire for a 50-Amp EV Charger
The 125% rule, 6 AWG vs 8 AWG copper, aluminum runs, voltage drop and GFCI for a 40 A or 48 A Level 2 charger.
HVAC / refrigeration
How to Check Superheat and Subcooling on an AC System
Which reading to charge by, where to clamp, and what high or low superheat and subcooling tell you about the charge.
5 min read · updated Oct 7, 2026How to Measure Total External Static Pressure
Two test ports, one manometer, and a number you compare to the data plate. How to measure TESP and read what it tells you.
5 min read · updated Oct 7, 2026How to Size an Air Conditioner for Your Home
BTU per square foot gets you a starting size; Manual J gets you the right one. Why bigger is worse and what the numbers mean.
Fire protection
How to Calculate Fire Alarm Battery Size (NFPA 72)
24 hours standby plus 5 minutes alarm, the 1.2 derating factor, standard battery sizes and a worked example that lands on a 12 Ah set.
5 min read · updated Oct 7, 2026How to Calculate NAC Voltage Drop: End-of-Line vs Point-to-Point
Panel minimum minus wire drop must leave the last appliance above its minimum. Lump-sum and point-to-point methods, with a worked example.
5 min read · updated Oct 7, 2026How to Use Sprinkler K-Factor to Find Flow and Pressure
Flow from pressure with Q = K√P, the 7 psi floor, and how the demand grows from the remote sprinkler back to the supply.
Construction
How Much Concrete Do I Need? Slabs, Footings and Piers
Length times width times thickness, divided by 27. Bags or a truck, how much waste to add, and how thick the slab should be.
5 min read · updated Oct 7, 2026How to Lay Out Stair Stringers: Rise, Run and Code Limits
From total rise to a marked 2x12: riser count, tread depth, stringer length, the IRC limits and the mistakes that make steps uneven.
Trucking
Rental property & mortgages
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