Blog
Practical guides and explainers about the calculators on the site. Written by the maintainer, cross-checked against primary sources.
Cross-locale capital gains and estate planning 2026: Brazilian US dual-jurisdiction framework
Cross-locale capital gains and estate planning Q1-Q2 2026 for Brazilian residentes US — Lei 14.754/2023 plus IN RFB 2180/2024 Brazilian offshore framework (15% uniform rate on offshore financial income regardless of distribution, 8% asset revaluation election during 2024 transition window), OBBBA 2025 PERMANENT estate exemption $15M individual / $30M MFJ with step-up basis at death intact, LC 227/2026 ITCMD valor mercado plus goodwill Brazilian impact, Lei 15.270/2025 PJ plus PF impact Brazilian residente US, 1967 Brazil-US tax treaty limited scope sustained (no broad coverage), FATCA Form 8938 plus FBAR per asset class compliance thresholds, IRC Section 877A exit tax for Brazilian formalizing US permanent residency (covered expatriate $2M net worth test, mark-to-market deemed sale, 2026 exclusion $910,000 vs 2025 $890,000), cross-asset stocks ETFs crypto real estate retirement dual-jurisdiction framework consolidando Posts #1-4 Batch 15.
Real estate tax strategy 2026: Section 121, Section 1031, depreciation recapture, and step-up basis
Real estate tax strategy Q1-Q2 2026 — Section 121 home sale exclusion sustained at $250k single / $500k MFJ with 24 of 60 months ownership and use requirements (not adjusted for inflation since 1997), Section 1031 like-kind exchanges restricted to real property post-TCJA 2017 with strict 45-day identification and 180-day closing deadlines plus Qualified Intermediary requirement, Section 1250 unrecaptured gain capped at 25% (lesser of marginal rate or 25%) with cost segregation reclassification opportunity, OBBBA 100% bonus depreciation made PERMANENT for property acquired after January 19, 2025 (TCJA phase-down reversed), NEW OBBBA qualified production property full expensing provision (construction beginning after January 19, 2025 and before January 1, 2029, placed in service before January 1, 2031), Section 199A QBI deduction made PERMANENT by OBBBA with NEW $400 minimum QBI deduction for eligible taxpayers in 2026 plus rental safe harbor 250 hours, real estate professional 750 hours plus material participation for passive activity loss treatment, $25,000 special allowance with MAGI phase-out $100k-$150k, step-up basis at death intact for taxable assets, OBBBA estate exemption $15M per individual / $30M MFJ permanent, cross-locale Brazilian residente US real estate Lei 14.754/2023 plus Form 8938 plus FBAR plus 1967 treaty limited scope.
Crypto tax reporting 2026: Form 1099-DA, wash sale pending, and cost basis methods
Crypto tax reporting Q1-Q2 2026 — Form 1099-DA broker reporting (gross proceeds since January 2025, cost basis required for transactions on or after January 1, 2026), Notice 2024-56 good-faith relief for 2025, Revenue Procedure 2024-28 mandatory per-wallet cost basis tracking (universal method eliminated, safe harbor expired with 2024 filing), wash sale rule IRC Section 1091 does NOT apply to crypto (property classification sustained), DeFi staking/lending ordinary income at dominion and control + capital gain on disposal, NFT collectibles 28% cap (long-term only) via IRS look-through analysis, mining/airdrops/forks ordinary income at receipt, Senate revoked DeFi broker inclusion in 2025 (decentralized exchanges and self-custody wallets NOT issuers of 1099-DA), cross-locale Brazilian residente US Lei 14.754/2023 + Form 8938 + FBAR threshold.
Retirement strategy 2026: Roth conversion ladder + OBBBA estate integration
Retirement strategy Q1-Q2 2026 — 401(k) limit $24,500 + $8,000 catch-up 50+ + $11,250 super catch-up 60-63 (SECURE 2.0), IRA limit $7,500 + $1,100 catch-up 50+, Roth IRA phase-out single $153k-168k / MFJ $242k-252k, NEW Roth Catch-Up Rule for High Earners 50+ earning >$150k FICA wages prior year must make catch-up on Roth basis effective January 1, 2026, HSA limits $4,400 single / $8,750 family + $1,000 catch-up 55+, RMD age 73 (2023-2032) shifting to 75 in 2033, Roth 401(k) no RMD requirement post-2024, inherited IRA 10-year rule with annual RMDs required when decedent died on/after RBD (2022 relief ending 2025+), mega backdoor Roth 401(k) up to total $70,000 annual, OBBBA estate exemption $15M/$30M permanent + step-up basis at death intact + Roth IRA inheritance tax-free, cross-locale Brazilian residente US Lei 14.754/2023 + Form 8938 + FBAR.
Capital gains optimization 2026: OBBBA framework + cross-asset strategy
Capital gains optimization Q1-Q2 2026 under OBBBA permanent framework — long-term rates 0%/15%/20% + NIIT 3.8% thresholds ($200k single / $250k MFJ, not inflation-adjusted since 2013), QSBS Section 1202 tiered exclusion post-OBBBA 50%/75%/100% (3yr/4yr/5yr+) with $75M gross asset threshold + $15M per-issuer cap (or 10x basis, greater) for stock acquired after July 4, 2025, QOZ original deferral ending December 31, 2026 with rolling 5-year deferral and 10% basis step-up for post-2026 investments, Form 1099-DA crypto reporting effective January 1, 2025 with broker basis reporting expanding 2026, wash sale rule does not apply to crypto in 2026 (legislative pending), Section 121 home sale exclusion $250k/$500k sustained, Section 1031 like-kind real estate only, step-up basis at death intact, OBBBA estate exemption $15M/$30M permanent, cross-locale Brazilian residente US dual-jurisdiction Lei 14.754/2023.
Weighted average: when arithmetic mean lies and how to fix it
How to calculate weighted average and when it matters: GPA, portfolio returns, blended interest rates, and the cases where simple averaging quietly produces the wrong answer.
Age calculator: how the math handles months, leap years, and time zones
How an age calculator handles the edge cases people forget: leap years, day-of-month rollovers, time zones, and the difference between "completed years" and "calendar age". With three real examples and the gotchas in legal and medical contexts.
Percentage calculator: the 3 formulas that cover 90% of cases
The three practical percentage formulas with worked examples (discount, salary raise, expense share) and the trap that makes a 20% raise plus 20% discount lose 4%, not return to the original.
W-2 vs 1099 self-employed 2026: tax math after OBBBA
OBBBA (July 2025) made Section 199A QBI deduction permanent. FICA wage base 2026: $184,500. Standard deduction 2026: $16,100 single / $32,200 MFJ. Worked example $100,000 income: W-2 vs 1099 within $3,000 net when deductions maximized. Decision framework with Q1-Q2 2026 data.
OBBBA + TCJA 2026: post-sunset reality for typical filers
OBBBA signed July 2025 made TCJA tax brackets, standard deduction, and Section 199A QBI deduction permanent. Child Tax Credit raised to $2,200. SALT cap raised to $40,000 (2025-2029). Estate exemption $15M/$30M permanent 2026. Cached "TCJA sunset" advice is structurally outdated.
Roth IRA vs Traditional 401(k): tax-optimization 2026 decision framework
Updated for 2026 IRS limits (Nov 2025 Notice 2025-67): 401(k) $24,500, IRA $7,500, catch-up $8,000, super catch-up $11,250 ages 60-63. SECURE 2.0 mandatory Roth catch-up threshold raised to $150,000. OBBBA July 2025 made TCJA brackets permanent. Multi-vehicle optimization across 401(k), IRA, Backdoor Roth, Mega Backdoor, HSA.
Capital Gains Tax Strategy 2026: post-OBBBA decision framework
Updated for 2026 IRS Rev. Proc. 2025-32 LTCG brackets ($48,350/$533,400 single; $96,700/$600,050 MFJ), OBBBA July 2025 changes to QOZ (extended indefinitely + new 5-year deferral) and QSBS Section 1202 (tiered 3/4/5-year holding period + $15M cap), NIIT bracket creep, Section 121 bracket creep, crypto wash sale status, and step-up basis estate planning integration.
Self-Employed Quarterly Estimated Tax 2026: safe harbor framework
Updated for 2026 quarterly deadlines (April 15, June 15, September 15, January 15 2027), IRS underpayment rates (Q1 7%, Q2 6%), 110% safe harbor for AGI > $150,000 ($75,000 MFS), and OBBBA new Schedule 1-A with 4 below-the-line deductions (tips $25,000, overtime $12,500, vehicle loan interest $10,000, senior bonus $6,000) affecting current-year safe harbor math.
401(k) loan vs. personal loan: the four hidden costs
Borrowing from a 401(k) at 8.25% looks cheaper than a 12% personal loan, but four hidden costs flip the math for most borrowers in 2026: opportunity cost, double taxation on interest, separation-event risk, and lost employer match. Decision framework with worked numbers.
HELOC vs. cash-out refinance in 2026: the rate-environment trap
The standard "cash-out refinance for home equity" advice was correct for the 2018-2022 rate environment. In Q2 2026 with 50.6% of US homeowners locked at sub-4% mortgages and current rates at 6.37%, cash-out refinance costs roughly 9× more than HELOC for typical extraction scenarios. Worked numbers and decision framework.
Auto insurance premium breakdown 2026: the 18 factors
US auto insurance averaged $2,285/year as of April 2026 per Experian. State variation: Vermont $1,624 to Louisiana $3,481. Premiums use 18-22 factors, but quote sites expose only 4-6. Guide to the 6 you can influence, the 6 you cannot, and the 6 aggregators hide.
Term vs whole life insurance 2026: the buy-term-invest math
Term life at age 35 for $500k costs $25-40/month per Q1-Q2 2026 rates; whole life costs $500-580/month for the same death benefit. Buy-term-invest-the-difference math validated against 2026 data, agent commission structure exposed, 4 scenarios where whole life is defensible.
HDHP+HSA vs PPO 2026: triple tax advantage math
IRS Rev. Proc. 2025-19 set 2026 HSA contribution at $4,400 single / $8,750 family + $1,000 catch-up. HDHP minimum deductible $1,700/$3,400; OOP max $8,500/$17,000. ACA enhanced subsidies expired end 2025 — Marketplace premiums up 114% average for subsidized enrollees in 2026.
Credit card payoff vs. debt consolidation: 2026 framework
Average US credit card APR is 21.00% in Q1 2026. Personal loan APR averages 12.27%. The math for debt consolidation looks obvious, but a 2023 TransUnion study found balances returned near previous levels 18 months after consolidating. Decision framework with worked numbers.
Maternity leave: United States vs Brazil compared (2026)
A side-by-side comparison of maternity leave in the US and Brazil in 2026. Federal entitlement, state-level expansions, paid vs unpaid, employer obligations, and what the gap actually means for working parents.
Auto loan trade-in equity: the four scenarios most calculators ignore
Online auto loan calculators treat trade-in value as a single positive number, but 30.9% of Q1 2026 trade-ins carry negative equity. This guide covers the four equity scenarios with worked numbers, the APR premium for rolled-in negative equity, and what conventional calculators miss in 2026.
Home affordability and after-tax income: why bank calculators understate burden in high-tax states
Bank affordability calculators ask for gross income because that is what underwriters use, but the gap between gross and take-home varies from roughly 28% in zero-income-tax states to 40% in high-tax metros. This guide breaks down the gap by state tier and shows how to use the calculator custom DTI mode to model post-tax sustainability properly.
Real-world MPG vs EPA sticker: why your fuel cost beats the projection
EPA fuel economy ratings come from dynamometer lab tests, not road testing. Real-world MPG averages 8-15% lower than EPA combined and can drop 25%+ in cold weather. This guide breaks down the EPA test cycles, the four conditions that widen the gap, and how to project realistic 5-year fuel cost.
Mortgage vs rent break-even: the six variables that move the math in 2026
The 5-year rule for buying versus renting is folk wisdom, not analysis. Real break-even depends on six variables: home price, mortgage rate, rent inflation, home appreciation, opportunity cost of down payment, and effective tax burden. Under Q2 2026 conditions, break-even has stretched well past the historical 5-7 year window, with high-cost metros pushing past 15 years.
Personal loan fixed vs variable rate: scenario math no single-input calculator can show
Conventional personal loan calculators model fixed-rate APR cleanly but cannot show variable-rate trajectory math. Variable-rate loans launch 0.5-1.5pp below fixed but transfer rate risk to the borrower. This guide walks through three Q2 2026 rate-trajectory scenarios with month-by-month math and shows when fixed beats variable mathematically vs when the variable premium pays off.
Student loan refinance vs forgiveness 2026: post-SAVE decision
The 8th Circuit eliminated SAVE on March 10, 2026. The new RAP plan extends forgiveness to 30 years on tiered AGI payments. This guide covers when refinancing federal to private wins now and when it permanently locks you out of forgiveness.
BMI, BMR, TDEE: explained without the myths
A clear breakdown of three numbers that get conflated all the time. What BMI does and does not measure, why BMR matters more than people think, and how TDEE actually drives a sane cutting or bulking plan.
401(k), IRA, Roth: the 2026 decision framework
A clear framework for choosing between 401(k) traditional, 401(k) Roth, IRA traditional, IRA Roth, and the mega backdoor Roth. 2026 contribution limits, employer match math, withdrawal rules, and the bracket arbitrage that drives the Roth-vs-traditional decision.
Emergency fund: how much and where to keep it
A practical guide to sizing and parking an emergency fund in 2026. The 3-6-12 month framework, where high-yield savings vs Treasury direct vs money market actually wins, and the failure modes that defeat the whole point.
Pregnancy due date methods: how the math actually works
The three methods used to estimate due date in 2026, Naegele rule, ultrasound dating, and IVF transfer date. Why they sometimes disagree, when each is most accurate, and what "due date" actually means.
Home Equity Loan vs HELOC: Which Fits You?
Home equity loans and HELOCs both tap your equity but work very differently. Compare fixed-rate lump sums vs revolving credit lines and see which costs less.
Mortgage vs renting: the real break-even math
The honest cost comparison that includes opportunity cost, maintenance, property tax, and how long you need to stay for buying to actually win.
Social Security claiming: when to file in 2026
A practical guide to deciding when to claim Social Security in 2026. Why 70 is usually the right answer, the math behind delayed retirement credits, spousal strategies, and the cases where filing early actually wins.
Simple vs compound interest: when each one actually wins
Compound interest wins almost always — but there are three specific cases where simple interest is what you are really dealing with. A plain-English comparison with numbers.
Compound interest: how it actually works
A plain-English explainer of compound interest: the formula, a worked example, three real-life uses, and five pitfalls. Runs in five minutes.
FIRE number: the 25× rule, explained
What the 25× rule really means, where it comes from (Trinity Study), five FIRE variants, and the numbers you need to plug into a calculator to find your target.
BMR vs TDEE: the calorie numbers that matter
What BMR and TDEE are, how three different formulas calculate them, and how to pick a daily calorie target for weight loss, maintenance, or gain.
Compound interest: the complete guide
Everything you need to know about compound interest: the formula, why floating-point breaks it, the rule of 72, after-tax and after-inflation math, and how to actually use it across savings, debt, and retirement.
The HSA strategy: how to actually use the triple tax advantage
How to use a Health Savings Account as a stealth retirement vehicle. The triple tax advantage explained, when HDHP makes sense, the receipt strategy, and the HSA-investing pitfalls most people miss.
Mortgage vs renting in 2026: the deep-dive break-even math
A real break-even analysis for buying vs renting in the 2026 US housing market. Closing costs, opportunity cost, HOA, property tax, the 5% rule, and the scenarios where renting actually wins on math.
When to refinance your mortgage in 2026
A practical decision guide for refinancing in 2026: break-even months, closing costs reality, rate-and-term vs cash-out, and the scenarios where it actually makes sense to pull the trigger.
W-2, 1099, S-Corp: a 2026 decision framework
How to think about choosing between W-2 employment, 1099 contractor work, and S-Corp election. Tax implications, the SE tax math, when S-Corp pays for itself, and the cases where staying W-2 wins.