Guides & how-tos
Practical answers with the math shown — every guide pairs with a free calculator. Written by Mohamed Zakrya.
Home Improvement
How Many Gallons Is My Pool? Average Depth and the Three-Part Floor
The mean of the shallow and deep ends is exact for one shape of floor, and most pools are not that shape.
August 13, 2026 · 9 min read
Home Improvement
How Many Pavers Do I Need? Pavers, Base, Bedding and Joint Sand
Four quantities come out of one measurement, and the paver count is the easy one — the base is where a patio is usually ordered short.
August 13, 2026 · 9 min read
Home Improvement
How Many Stairs Do I Need? Risers, Treads and the Code Edge
You do not choose the riser height. You choose how many, and the height is whatever the division hands back.
August 13, 2026 · 9 min read
Home Improvement
How Much Carpet Do I Need? Runs, Seams and the Roll Width
A 280 sq ft room takes 352.8 sq ft of carpet, and only 14 of those extra feet are the trim allowance.
August 13, 2026 · 9 min read
Home Improvement
How Much Insulation Do I Need? R-Value, Inches and Bags
The target is an R-value, the depth is inches, and the purchase is bags — and bags never come from the inches.
August 13, 2026 · 9 min read
Home Improvement
How Much Roofing Do I Need? Squares, Bundles and the Pitch Multiplier
The one material on a house where the area you measure and the area you buy are different numbers, and the arithmetic that separates them.
August 13, 2026 · 8 min read
Electricity & Energy
What Size Wire Do I Need? Voltage Drop Over a Long Run
The current goes out and comes back, so a 100 ft run is 200 ft of copper — and moving to 240 V helps twice over.
August 13, 2026 · 9 min read
Home Improvement
How Much Flooring Do I Need? Boxes, Waste & Room Math
Floor area is the easy part. Waste tiers, box coverage, and rounding up are where the order goes wrong.
August 13, 2026 · 7 min read
Travel
How to Claim a Trip Back: Mileage or Actual Cost, Per Diem or Receipts
A method-first guide to choosing vehicle, meal, and lodging claims that match the claimant, governing rules, and available evidence.
August 12, 2026 · 11 min read
Home Improvement
Sod or Seed: Which One Your Site Will Actually Let You Use
The five site conditions that settle a lawn-establishment method before cost gets a vote, and how to compare the two orders once they do.
August 12, 2026 · 9 min read
Math
How to Find the Volume of Hollow, Partial, and Composite Solids
A decomposition-first guide to pipes, frustums, domes, and partly filled tanks, with formulas and checks for avoiding geometric and unit errors.
August 12, 2026 · 12 min read
Math
How to Compare Two Data Sets: Center, Spread, and Relative Difference
A practical workflow for deciding whether two sets are comparable, describing their typical values and variation, and reporting differences without overstating them.
August 11, 2026 · 10 min read
Utilities
Putting JSON in a URL: Validate, Minify, Percent-Encode, or Base64url?
A decision guide for flattening, encoding, checking, and safely transporting JSON in a query string.
August 11, 2026 · 9 min read
Dates & Time
How to Schedule a Meeting Across Time Zones Without DST or Date-Line Mistakes
A workflow for choosing, validating, and communicating a meeting time when offsets, calendar dates, and daylight-saving transitions can differ.
August 11, 2026 · 10 min read
Finance & Math
How Are Loan Payments Calculated? Amortization, Explained
One level payment, front-loaded interest — the formula worked by hand, the two levers you control, and why the smaller payment is often the costlier loan.
July 23, 2026 · 13 min read
Finance & Math
How Does Inflation Work? The Math That Shrinks Money
One growth factor, two answers — what today's money will buy later, and how many future dollars it takes to keep up.
July 23, 2026 · 13 min read
Finance & Math
How Is Sales Tax Calculated? Rates, Rules, and the Reverse Math
The combined-rate reality, the one-multiplication forward formula, and the division that pulls the tax back out of any total.
July 23, 2026 · 13 min read
Electricity & Energy
How Many Solar Panels Do I Need? Sizing From Your Real Usage
Daily usage divided by what one kilowatt makes in a day, why sun hours dominate the count, and the wattage trade that saves a tight roof.
July 23, 2026 · 13 min read
Electricity & Energy
How Much Does Heating Cost? By Fuel, Per Month, With Math
The watts-times-hours formula, the $63 default month, why every 1,500 W heater costs the same to run, and where gas and heat pumps land.
July 23, 2026 · 13 min read
Electricity & Energy
How Much Does It Cost to Charge an EV? Home vs Public, Per Mile
The three-line formula, the losses you pay for but never keep, and why home charging beats public by two to four times.
July 23, 2026 · 13 min read