47 guides
The Journal
Plain-English guides that work through the math behind everyday money, business, health and home-energy decisions, each with a worked example and a calculator to run your own numbers.
"No Tax on Overtime" 2026: What the Deduction Covers
The OBBBA lets you deduct qualified overtime pay through 2028: only the FLSA premium half, up to a cap, below certain income levels.
"No Tax on Tips" 2026: The $25,000 Deduction, Explained
Tipped workers can deduct qualified tip income through 2028: up to $25,000, with an income phase-out and an occupation eligibility list.
The $6,000 Senior Deduction 2026: How It Stacks
Taxpayers 65+ get a new $6,000 federal deduction through 2028, on top of the existing 65+ standard deduction, with its own phase-out.
Self-Employment Tax and Quarterly Payments, Explained
The 15.3% self-employment tax surprises new freelancers. How it is calculated, what offsets it, and how to size your quarterly payments.
Social Security Claiming Age: The Break-Even Math
Claim at 62, 67, or 70? The right answer depends on a break-even age most calculators skip. Here is the actual math, worked by hand.
RMD Rules 2026: Required Age, Formula, and the April 1 Trap
SECURE 2.0 split the RMD starting age by birth year. The formula, and the deadline mistake that costs people two RMDs in one year.
Roth vs. Traditional: It's a Bet on Your Future Tax Rate
Neither account is universally better. The math shows exactly why it comes down to one comparison: your tax rate today versus your tax rate when you withdraw.
401(k) Limits 2026: $24,500, Catch-Ups, Per-Paycheck Math
The 2026 401(k) limit is $24,500, with bigger catch-ups at 50 and 60-63. Per-paycheck amounts to max out, plus the new Roth catch-up rule.
401(k) Employer Match: How It Works and How People Miss It
Match formulas like "50% of 6%" can mean less than they sound. How to read yours, and the maxing-out mistake that forfeits part of it.
401(k) Balance by Age: How Much Should You Have Saved?
Fidelity's rule of thumb: 1x salary by 30, rising to 10x by 67. What that means in dollars, and the savings rate that gets you there.
The Real Cost of Cashing Out a 401(k) Early
A $10,000 early withdrawal can leave you $6,300 after penalty, tax, and withholding. Plus the rule of 55 and the loan alternative.
Section 25D Solar Tax Credit Ended: What's Left in 2026
The 30% credit for homeowner-owned solar and batteries ended for installs completed after Dec 31, 2025. What that does to payback and what remains.
AI Agent and Tool Costs for a Small Team in 2026
Per-seat AI prices look small until a team stacks overlapping tools. 2026 list prices, usage-based billing and a worked audit of an 8-person team.
Car Loan Interest Deduction 2026: Rules and Limits
Deduct up to $10,000 of interest on a loan for a new U.S.-assembled vehicle, 2025 through 2028. Who qualifies, the phase-out, and what it saves.
Waist-to-Height Ratio vs BMI: What Each One Tells You
BMI compares weight with height. Waist-to-height ratio shows fat around the middle. How to measure it, the NICE bands, and a worked example using both.
HSA as a Retirement Account: How It Works in 2026
An HSA can work as a retirement account: deductible in, untaxed growth, tax-free medical withdrawals, IRA-like rules after 65. 2026 limits and an example.
Debt Avalanche vs. Snowball: Which Payoff Method Is Better?
Avalanche pays the least interest; snowball clears accounts sooner. A worked example shows a $383 gap, and what research says about sticking with it.
Extra $100 a Month on Your Mortgage: How Much It Saves
On a $350,000 loan at 6.5%, an extra $100 a month saves $62,627 in interest and ends the loan 3.5 years early. See the math and when to start.
FIRE Number: How Much You Need to Retire Early
Your FIRE number is yearly spending divided by your withdrawal rate. Here is where 4% comes from, why early retirees often use 3.5%, and a worked example.
Mortgage Recast: How It Works and How It Compares to a Refi
A recast lowers your payment after a lump-sum principal payment and keeps your rate. See the math on a $40,000 recast and how it compares to a refinance.
How to Protect Your Savings From Inflation in 2026
Prices rose 3.4% in the year to August 2026. How to work out your real return, and how I bonds, TIPS, stocks and fixed-rate debt compare.
Mortgage Interest vs. Inflation: Your Real Borrowing Cost
At a 7.03% mortgage rate and 3.4% inflation, the real cost of borrowing is about 3.5%. How to calculate it, and whether to prepay or invest.
5 Tax Deductions for Freelancers and the Self-Employed
Home office, QBI, health insurance, retirement plans and half of SE tax: what each is worth in 2026, and which lower self-employment tax.
How Much Emergency Fund Do You Need? 3 to 12 Months
Start from 3 to 6 months of essential expenses and adjust for your income and household. A worked $15,000 example, and where to keep the money.
SaaS TCO: How to Calculate What a Subscription Really Costs
SaaS total cost of ownership adds setup, training, integration and admin time to the license fee. Here is the formula and a worked example.
Hiring vs. Automation ROI: How to Compare the Costs
A hire costs about 1.35 to 1.43 times salary. Automation costs a build plus software and review time. Here is the break-even math with a worked example.
What Is a Good ROAS? How to Find Your Break-Even ROAS
A good ROAS is one above your break-even ROAS, which is 1 divided by your margin. Here is the formula, typical margins by industry and a worked example.
LTV:CAC Ratio and CAC Payback: How to Calculate Both
LTV:CAC compares what a customer is worth with what it cost to win them. Here are both formulas, the common 3:1 and 12-month guidelines and a worked example.
The ROI of GTD and Other Productivity Systems
No study we found shows GTD saves a fixed number of hours. Here is how to estimate your own net time saved, what switching research says and a worked example.
Weight Loss Plateau: Why It Happens and What to Check
Weight loss slows because a smaller body burns less and appetite rises. Why plateaus happen, a worked calorie example, and what to check before changing course.
How Much Protein Do You Need to Build Muscle?
Research points to about 1.6 g of protein per kg of body weight a day for muscle gain. What that means in grams, and whether 1 g per pound is needed.
Net Zero Home Upgrades: What to Do First in 2026
Seal and insulate first, then heating and cooling, then solar sized to the smaller load. The order, the 2026 tax credit changes, and a sizing example.
Is a Home Battery Worth It in 2026? Sizing and Payback
Home batteries installed after 2025 get no federal credit. How to size one for outages and estimate payback from bill savings, with the math shown.
Does Remote Work Reduce Your Carbon Footprint?
Usually yes, if it replaces a car commute. A worked example weighs commute savings against extra home energy, plus what research found about hybrid work.
Side Hustle Hourly Rate: How to Calculate Your Real Profit
Your real side hustle hourly rate is profit after expenses and tax divided by every hour you spend, including admin. Here is the formula and a worked example.
EV vs. Gas Car Savings in 2026: Break-Even and Range
At 2026 U.S. average prices, home charging costs about 5 cents a mile vs. 18 for a 25 mpg car. How to find your break-even now the EV credit is gone.
Rent vs. Buy in 2026: How to Compare the Real Costs
Whether buying beats renting depends on rent, your mortgage rate and how long you stay. A worked $350,000 example at 7% with break-even years.
AI Agents vs. Hiring: How to Compare the Costs
Compare a hire's loaded cost with an AI tool's fees, setup and review time. In our example, 10 people save 1,326 net hours a year, 0.64 of a full-time role.
Debt Consolidation Loans: Why a Lower Payment Can Cost More
$20,000 at 12% costs $3,914 in interest over 3 years but $9,657 over 7. How loan term, fees and new card spending decide whether consolidating pays.
Is a Certification Worth It? How to Calculate the ROI
Add the exam, course and study hours, then weigh them against a raise you may not get. BLS earnings data and a worked payback example.
Fiber, Gut Health and Weight: How Much Fiber per Day?
A common target is 14 g of fiber per 1,000 calories, or 28 g at 2,000 calories. What fiber does for weight and gut health, and how to add it without discomfort.
When to Refinance in 2026: The Break-Even Calculation
Divide closing costs by monthly savings to find your break-even month. A worked 7.875% to 6.75% example, and what a new 30-year term costs.
Remote Work Savings: What Your Commute Really Costs
Using the IRS mileage rate and Census commute data, a 12-mile commute costs about $5,810 a year in cash, the same as a $7,747 raise at a 25% tax rate.
Burnout Prevention ROI: How to Build the Business Case
Gallup puts the cost of replacing an employee at half to twice their salary. Here is a break-even formula for a burnout prevention program and a worked example.
How Sleep Affects Fat Loss and Appetite
Short sleep is linked to eating more and losing less fat on a diet. What the studies found, a worked calorie example, and how much sleep adults need.
Saving for Retirement Starting at 40: The Math to 65
Starting at 40 still leaves 25 years to compound. See what $1,000 a month grows to by 65, what catch-ups add at 50, and the 2026 limits.
How to Cut Commute Emissions: Car, EV, Transit or Bike
Transportation is the largest U.S. emissions source. Compare fewer trips, an EV, transit and biking for a 12-mile commute, with the math shown.
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