Deduction strategy

Itemized vs standard deduction calculator

An itemized vs standard deduction calculator answers a question most people guess at: do your charitable gifts, mortgage interest, and state & local taxes (SALT) add up to more than the standard deduction? Since the standard deduction roughly doubled in 2018, most households take it — but homeowners in higher-tax states, bigger givers, and higher earners often leave real money on the table by not checking. Coastline runs the comparison the way a real return does: it computes both, takes the larger, and shows you which won — every single year of your plan.

$111,921 vs $32,200 — itemized vs standard for this household

A married couple in California earning $400,000 with a $900,000 home and 10% charitable giving itemizes $111,921 — charitable gifts $25,358, mortgage interest $46,563, SALT capped at $40,000 — about 3.5× the $32,200 standard deduction.

Who itemizes? Four real households

Same engine, four situations — the deciding factors are a mortgage, state taxes, and giving:

Household → itemizable deductions vs the standard deduction (2026, first projection year)
Household	Itemizable	Standard	Winner
MFJ · CA · $400k · $900k home · 10% giver	$111,921	$32,200	Itemize
MFJ · CA · $400k · $900k home · no giving	$86,563	$32,200	Itemize
MFJ · AZ · $200k · $450k home	$33,232	$32,200	Itemize
Single · TX · $110k · renter	$0	$16,100	Standard

Notice the second row: even with zero charitable giving, the California homeowners itemize on mortgage interest + SALT alone. And the Arizona couple squeaks past the standard deduction by about $1,032 — close enough that a single extra donation flips entirely into tax savings.

The three big itemized deductions (and their caps)

Charitable gifts. Cash donations are deductible above a 0.5%-of-AGI floor (new for 2026), up to 60% of AGI. If you already itemize, every additional dollar of giving reduces taxable income.
Home mortgage interest. Interest on up to $750,000 of acquisition debt. Early in a mortgage, most of the payment IS interest — a $720,000 loan at 6.5% pays roughly $46,563 of interest in year one.
SALT — state & local taxes. State income tax plus property tax, currently capped at $40,000 (with a phase-down for very high incomes, and scheduled to revert to $10,000 in 2030). High-tax-state homeowners usually hit the cap.

Why a calculator beats a rule of thumb

The itemize-or-not decision changes over time: mortgage interest shrinks as the loan amortizes, the SALT cap is scheduled to drop sharply in 2030, and your giving and income move. A snapshot answer for this year can be the wrong answer for the next decade. Coastline recomputes the comparison every year of your projection — so you see not just whether you itemize today, but when you'll stop, and what that does to your after-tax savings over a lifetime. The year-by-year math shows the winning deduction and each component.

Why Coastline's version is different

Most free calculators hand you a single headline number with the assumptions hidden. Coastline is built the opposite way:

Real tax math, not a flat rate. It applies federal and state income tax, long-term capital-gains rules, and account-by-account treatment (taxable, traditional, Roth) — in both your working years and retirement.
The whole journey. It models accumulation (saving and investing) and drawdown (spending it down), so you see how the plan connects end to end, not just one half.
The math is shown. Every figure has a click-through breakdown of how it was computed — a level of transparency even paid tools rarely expose.
US and Canada. It natively handles Canadian plans (RRSP, TFSA, CPP, OAS) alongside US accounts, which most calculators ignore.
Free, no signup. No account, no email, no account-linking. Your inputs run the projection and are then discarded.

Educational, not tax advice. The comparison uses federal rules for the year shown (charitable floor and 60% cap, the $750,000 mortgage-interest cap, the SALT cap and its scheduled 2030 reversion); state itemization rules differ and are not modeled. Confirm your specific return with a tax professional.

Run this with your real numbers

Enter your income, home, state, and giving — the projection takes the larger deduction each year and shows the math.

Open the free calculator →

Common questions

Should I itemize or take the standard deduction?

Take whichever is larger — that is the whole decision. Add your charitable gifts, home mortgage interest, and state & local taxes (capped); if the total beats your standard deduction, itemizing saves you tax. Coastline runs this comparison automatically for every year of your plan.

What counts toward itemized deductions?

The big three are charitable donations (above a 0.5%-of-AGI floor, up to 60% of AGI), home mortgage interest on up to $750,000 of loan principal, and SALT — state income plus property taxes, currently capped at $40,000 and scheduled to revert to $10,000 in 2030. Medical expenses above a high AGI floor can also count.

Do charitable donations reduce my taxes if I take the standard deduction?

Generally no — cash gifts only reduce federal tax when you itemize. That is why the comparison matters: a giver whose total deductions sit just below the standard deduction gets no federal tax benefit, while one dollar past the threshold starts saving at their marginal rate.

Why does the answer change from year to year?

Because the inputs move: mortgage interest falls as the loan amortizes, the SALT cap is scheduled to drop in 2030, and income, giving, and the inflation-indexed standard deduction all shift. Coastline recomputes the winner every projection year rather than freezing this year’s answer.