Canadian mortgage quotes: the compounding convention matters ↗
Convert a semiannual nominal mortgage quote to a monthly rate before estimating payments. See why dividing the quoted rate by twelve can differ.
Updated 2026-10-18A LITTLE UNDERSTANDING
The method matters.
29 practical guides for the questions behind your calculations. Follow a worked example, check the assumptions, then try the linked tools with your own inputs.
Borrowing
Developer & data
Clean CSV without losing its meaning ↗
Parse quoted cells, filter and sort deliberately, and inspect blanks and formula escaping before using an exported table.
Updated 2026-10-17Choose between CSV merge and join ↗
Append compatible tables or match records by a key, and diagnose missing matches, duplicate keys and unexpected row counts.
Updated 2026-10-17Select and redact JSON with explicit paths ↗
Use JSON Pointer escaping, distinguish arrays from objects and review the complete output before sharing redacted data.
Updated 2026-10-17Distinguish characters from UTF-8 bytes ↗
Understand why counts, normalization, Base64 and hexadecimal representations can have different lengths for the same text.
Updated 2026-10-17Money & borrowing
Compare loans beyond the monthly payment ↗
Compare payment, term, fees and total cost using the same principal. Learn why a smaller payment can still cost more.
Updated 2026-10-17Find average purchase cost from investment lots ↗
Calculate units purchased and weighted average cost, and understand why averaging quoted prices can give the wrong answer.
Updated 2026-10-17Explore savings and retirement assumptions ↗
Compare fixed-return scenarios and an income-gap target without treating a return or withdrawal assumption as a promise.
Updated 2026-10-17Plan a mortgage budget and balloon payment ↗
Translate an entered debt ratio into a payment budget, then distinguish amortizing, interest-only and balloon loans.
Updated 2026-10-17Use a portfolio rebalancing worksheet ↗
Turn target weights and current values into a transparent worksheet while keeping tax and trading costs outside the model.
Updated 2026-10-17Understand refinance break-even ↗
Separate monthly fee recovery from lifetime loan cost, and check whether fees are paid upfront or added to the balance.
Updated 2026-10-17Build a debt snowball and avalanche comparison ↗
Prepare a debt list, choose one fixed monthly budget and compare two payoff orders with a downloadable schedule.
Updated 2026-10-17Home & construction
Build a cutting list with kerf and offcuts ↗
Prepare cut requests, understand first-fit packing and reserve material for the physical cutting details the model excludes.
Updated 2026-10-17Turn dimensions into material quantities ↗
Keep volume, wet product yield, brick modules and waste allowances separate when preparing a materials purchase estimate.
Updated 2026-10-17Dates & time
Separate calendar dates, holidays and meeting instants ↗
Choose the correct model for working-day counts, monthly recurrences, invoice dates and international meeting conversions.
Updated 2026-10-17Electronics & energy
Connect appliance energy, cost and battery runtime ↗
Distinguish watts, watt-hours and amp-hours, then check usage assumptions before estimating an electricity charge or runtime.
Updated 2026-10-17Regional finance
GST and VAT: net, gross and recoverable tax ↗
Learn why adding tax, extracting included tax and recovering input tax are three separate calculations, with worked GST and reverse-charge examples.
Updated 2026-10-18Why UK property purchase taxes differ by region ↗
Compare standard SDLT, LBTT and LTT using the same price, then check the reliefs and surcharges each simple estimate leaves out.
Updated 2026-10-18Business & selling
Separate reorder point, safety stock and order quantity ↗
Use a stock trigger, uncertainty buffer and order-size model for their different purposes, with consistent demand and time units.
Updated 2026-10-17Read ROAS alongside conversion and contribution ↗
Connect ad spend, attributed revenue and contribution margin without treating ROAS as net profit or proof of incremental sales.
Updated 2026-10-17Set a selling price after fees and target margin ↗
Solve for a price that covers entered costs and payment fees, and distinguish margin from markup.
Updated 2026-10-17Accounting
Current, quick and cash ratios: what each includes ↗
Compare three liquidity measures without mistaking inventory or unpaid invoices for immediately available cash. Work through the same balance sheet.
Updated 2026-10-18Math & statistics
Check numeric matrix and polynomial results ↗
Prepare matrices and coefficient lists, then use substitution and convergence checks to assess a numeric answer.
Updated 2026-10-17Check data conventions before interpreting statistics ↗
Use bins, moving averages, percentiles and regression for different purposes, and inspect ordering and boundary assumptions.
Updated 2026-10-17Practical methods
Percentage, margin, or markup? ↗
Three similar-looking rates that answer different questions.
Updated 2026-10-16When units look almost the same ↗
A few small labels can make a large difference.
Updated 2026-10-16Physics
Physics calculators: check units and ideal assumptions ↗
Get useful answers from projectile, pressure, gas and lens formulas by checking SI units, sign conventions and the conditions each model assumes.
Updated 2026-10-18Everyday arithmetic
Scale quantities without assuming everything scales ↗
Scale ingredient quantities and count planting positions while recognizing edge effects and non-linear process changes.
Updated 2026-10-17Units
Specialist unit conversions: prefixes and conventions ↗
Avoid confusing charge with energy, US gallons with Imperial gallons, and dynamic viscosity with kinematic viscosity when converting technical units.
Updated 2026-10-18