Guides

A calculator answers a question; it rarely explains it. These guides take one question each and work through it with numbers produced by the same engine the tool runs - the arithmetic is on the page, the sources are listed, and each guide ends by naming what it does not cover.

Each guide is written by a dedicated author, answering a real question the calculators raise but do not answer. When one appears here, the tool it explains already exists - so you are not reading a page generated ahead of a need, but one that answers a real question in numbers you can check.

What is here

• Child Support Guidelines - Whose Table Applies

  A child support number is a state’s own table applied to a state’s own base - a flat share, a bracket stack, a printed row or a worksheet. This guide shows each shape and where the costs enter.

  Published 2026-11-06 · Last reviewed 2026-11-06

• Paycheck Tax Assumptions - Brackets and FICA

  A paycheck is built in a fixed order: pre-tax deductions, the annual ladder, FICA on wages, then the state rate you supply. This guide shows what each line assumes.

  Published 2026-11-05 · Last reviewed 2026-11-06

• Home Affordability - Debt-to-Income Solved Backwards

  Two ratios set a monthly budget; property tax, insurance and HOA dues then have to be solved for, because the price behind them is the unknown. The result is a ceiling, not a recommendation.

  Published 2026-11-05 · Last reviewed 2026-11-06

• Tip Splitting - Why the Shares Differ by a Cent

  A tip needs a base before it needs a percentage, and a split needs a rule for the cents. The leftover cent has to go somewhere, and the page names who pays it.

  Published 2026-11-04 · Last reviewed 2026-11-06

• Password Entropy - Bits, Words and the Browser

  A strength number is arithmetic on a keyspace, not a measurement of a person. This guide shows the formula, its blind spot for words, and where the randomness comes from.

  Published 2026-11-03 · Last reviewed 2026-11-06

• Markdown Dialects - Round Trips and Raw HTML

  Two dialects, two directions, one trust boundary. This guide explains the switches, the read-back check, and why raw HTML and javascript: links are refused by default.

  Published 2026-11-03 · Last reviewed 2026-11-06

• Merge PDF - What Survives a Browser Merge

  A merge copies page objects, not pixels - which is why the text stays selectable, the bookmarks do not come along, and the tab needs room for two copies.

  Published 2026-11-02 · Last reviewed 2026-11-06

• PDF Page Numbers - Content, Not Annotation

  A page number can be page content or an annotation, and the two behave differently in search, printing and every editor. The crop box then decides where it lands.

  Published 2026-11-02 · Last reviewed 2026-11-06

• Percentage Change - Change Rate Against Difference

  Change is measured from where you started; difference is measured between two values with no base. The gap between them is most percentage arguments.

  Published 2026-11-01 · Last reviewed 2026-11-06

• Credit Health - Utilization, Scores and Charge-Offs

  A score, a utilization ratio and a charge-off are three different readings of one credit file. This guide prices the ratio, runs the minimum-payment schedule and grows an unpaid balance to the charge-off point.

  Published 2026-10-31 · Last reviewed 2026-10-31

• Auto Insurance and Medicare - Two Bills You Cannot Skip

  Two compulsory insurance bills, priced by rules rather than shopping. This guide checks a real auto quote against a state floor and sweeps both Medicare paths across a year of services.

  Published 2026-10-31 · Last reviewed 2026-10-31

• Home Equity and Property Tax - What the House Costs

  A house is an asset and a bill at the same time. This guide prices a HELOC draw, a HECM principal limit and an annual property tax bill from the same engines the tools run.

  Published 2026-10-30 · Last reviewed 2026-10-30

• Mortgage Costs - APR, Closing Fees and Loan Types

  The advertised rate is only the first price on a mortgage. This guide folds fees into an APR, adds up the cash at closing, and compares what FHA insurance and the VA funding fee do to the monthly payment.

  Published 2026-10-28 · Last reviewed 2026-10-28

• Retirement Accounts - The Tax-Year Choice

  A retirement account chooses the year the tax is paid rather than avoiding it. This guide compares Roth and traditional at the same contribution, finds the break-even rate, and prices one year of a pre-tax deduction.

  Published 2026-10-26 · Last reviewed 2026-10-26

• COBRA, HSA and Disability - The Safety Net in Numbers

  A job loss, a high-deductible plan and a disability each need a different kind of cushion. This guide prices the COBRA premium, the HSA room and the SSDI benefit from the same engines the tools run.

  Published 2026-10-24 · Last reviewed 2026-10-24

• Payroll Extras - Bonus, Overtime and Tips

  A bonus, an overtime hour and a tip each reach the paycheck by a different route. This guide prices all three, then adds the employer-side payroll tax that never shows on a payslip.

  Published 2026-10-22 · Last reviewed 2026-10-22

• Gig and Freelance Taxes - From Billed to Kept

  Contract income has nothing withheld, so the freelancer pays both halves of FICA and an income tax on top. This guide follows one 1099 year from billed revenue to the quarterly bill.

  Published 2026-10-20 · Last reviewed 2026-10-20

• Sales Tax and SALT - What the Receipt and Schedule A Take

  Sales tax rides on the price you pay; the SALT deduction is capped and phased down. One is arithmetic at the till, the other a worksheet on Schedule A.

  Published 2026-10-18 · Last reviewed 2026-10-18

• Self-Employment and Home Office - The Tax on 1099 Work

  A freelancer pays both halves of FICA, then can take back part of it through a home office and mileage deduction. Two deductions, one 15.3 percent bill, priced here.

  Published 2026-10-15 · Last reviewed 2026-10-15

• Tax Brackets and Withholding - The Last-Dollar Rate

  A bracket prices the next dollar, not the whole salary. This guide walks one salary band by band, then shows how a W-4 or a quarterly estimate keeps withholding from missing.

  Published 2026-10-12 · Last reviewed 2026-10-12

• Family Tax Credits - CTC and EITC That Pay Back

  A working family can owe nothing and still get money back: the earned income credit and part of the child tax credit are refundable, so they come back even when the tax bill is zero.

  Published 2026-10-09 · Last reviewed 2026-10-09

• Itemized vs Standard - When the Standard Deduction Wins

  The standard deduction wins for most filers because mortgage interest, taxes and charity rarely add up to it - and when they do, SALT, medical and charity limits can cut them back before they count.

  Published 2026-10-06 · Last reviewed 2026-10-06

• Estate and Gift Tax - One Shared Lifetime Exemption

  A gift today and an estate at death meet at the same $15,000,000 lifetime exemption and the same 40 percent rate above it - so what you give away now is what is no longer in your estate later.

  Published 2026-10-01 · Last reviewed 2026-10-01

• Capital Gains - Stocks, Homes and Crypto

  The tax on a gain has no single rate: holding period and your other income decide it, a home adds a $250,000 or $500,000 exclusion, and long-term crypto rides the same ladder.

  Published 2026-09-28 · Last reviewed 2026-09-28

• Child Support - When Income Is Not Fully Counted

  The headline percentage is only half the rule; the base it multiplies - net resources, capped - is the half most people get wrong.

  Published 2026-09-23 · Last reviewed 2026-09-23

• Alimony - Bridge-the-Gap vs Rehabilitative

  Bridge-the-gap support patches the transition and stops at 2 years; rehabilitative support pays to get self-supporting and stops at 5 - but neither has an amount formula at all.

  Published 2026-09-23 · Last reviewed 2026-09-23

• Child Support - A Rate That Falls on Bigger Incomes

  The share printed at the top of the table is only the first bracket’s. On a tiered schedule the effective rate falls as income rises - 16 percent on the first dollars, 4 percent above.

  Published 2026-09-22 · Last reviewed 2026-09-23

• Child Support - A Table Split by Two Incomes

  The figure comes from a row in a combined-income table, not a rate, and it is divided by how the two parents’ incomes compare - the second income is not optional arithmetic in Virginia.

  Published 2026-09-22 · Last reviewed 2026-09-23

• Alimony - What a 35 Percent Ceiling Means

  A statutory maximum is not an award: one ceiling comes from the difference in net incomes, another from the length of the marriage, and need is neither.

  Published 2026-09-21 · Last reviewed 2026-09-22

• Social Security - The Claim Age That Sets Your Payment

  Claim at 62 and the check is 70 percent of the primary insurance amount; claim at 70 and it is 124 percent. The start age is the biggest lever on the page, and the whole range is one table.

  Published 2026-09-21 · Last reviewed 2026-09-23

• Home Affordability - A Payment, Not a Price

  The answer to how much house is a monthly payment, not a sticker: a lender caps it at the smaller of 28 percent for housing and 36 percent for all debts, and the price is whatever that payment buys. For a $90,000 household, the front-end rule binds.

  Published 2026-09-21 · Last reviewed 2026-09-23

• Deductible - What a Health Plan Really Costs

  Two plans can share a deductible and differ by thousands in the year you get ill. The break-even spending level - and the HSA that changes the high-deductible column - is the real comparison.

  Published 2026-09-20 · Last reviewed 2026-09-23

• Retirement Savings - The Cost of Starting Late

  A late start is not a short start. The monthly deposit needed to reach a goal multiplies with each lost year, because each missing year is not one deposit but one fewer year of compounding.

  Published 2026-09-20 · Last reviewed 2026-09-23

• Life Insurance - The Number DIME Produces

  The cover a family needs is a sum, not a multiple. Debts, income, mortgage and education add up to one number, and a home with a mortgage and two college-bound children can need more than double the "ten times income" shorthand.

  Published 2026-09-20 · Last reviewed 2026-09-23

• Marginal Tax Rate - Why a Raise Never Cuts Take-Home

  The bracket a raise crosses applies to the dollars above the line, not to the income below it - the same arithmetic that makes the headline rate and the effective rate two different numbers.

  Published 2026-09-17 · Last reviewed 2026-09-22

• Refinance Break-Even - What a Rate Cut Is Worth

  The lower payment is only a saving after the closing costs are earned back, and restarting the term can cost more than the rate saves. The break-even month is the number to argue about.

  Published 2026-09-17 · Last reviewed 2026-09-23

• Lease vs Buy - What the Resale Value Decides

  Two monthly figures look comparable but measure different things; the lease-vs-buy answer is the resale value, restated here as the exact percentage that flips the decision.

  Published 2026-09-17 · Last reviewed 2026-09-23

• Debt Payoff Order - Snowball Against Avalanche

  Both orders pay every minimum and then throw the rest at one debt. Which debt that is decides the interest bill - by less than most people expect, and never by more than the budget does.

  Published 2026-09-16 · Last reviewed 2026-09-22

• Minimum Payments - What the Minimum Really Costs

  The minimum is a percentage of the balance plus the month interest, so it shrinks every month you pay it - which is what stretches a payoff over years.

  Published 2026-09-16 · Last reviewed 2026-09-22

• Extra Payment - What a Mortgage Payoff Buys

  The reward for paying a mortgage down early never appears on a statement - it arrives years later. Here is the time and interest one recurring extra payment buys, priced by the engine the calculator uses.

  Published 2026-09-16 · Last reviewed 2026-09-23

• 401(k) Rollover - The 60-Day Rule in Numbers

  An indirect rollover looks like a withdrawal the moment the check is made out to you - here is what that mistake costs, priced by the same engine the calculator uses.

  Published 2026-09-15 · Last reviewed 2026-09-21

• Solar Payback - What the Utility Price Buys

  The number that decides a system is not the sticker price, it is the cost per kilowatt-hour it produces against what the grid charges - and both change every year.

  Published 2026-09-15 · Last reviewed 2026-09-21

• Total Interest - Why the Rate Is Not the Cost

  The interest rate is a price per year; the cost of a loan is a price per year times the years. This guide separates the two with the amortization engine.

  Published 2026-09-15 · Last reviewed 2026-09-21

Also on this site

• Glossary - the words these tools use, defined in one sentence each.
• Methodology - the formulas, rounding rules and default assumptions behind every calculator.
• All tools - the calculators each guide sends you to.

Guides are explanations, not advice. Read the full disclaimer.