How to Use This Tool
Enter your deductions and the tool takes the larger of the two routes. The bunching figure at the bottom is usually the interesting one.
You get one or the other, not both
Every filer takes either the standard deduction or the total of their itemised deductions, whichever is larger. For 2026 the standard deduction is:
- $16,100 single
- $32,200 married filing jointly
- $24,150 head of household
Anyone aged 65 or over adds a further amount — $2,050 for a single filer, or $1,650 per qualifying spouse on a joint return.
The important consequence: itemised deductions below the standard amount are worth nothing. Not a reduced benefit — zero. A $3,000 charitable gift in a year when your itemised total comes to $20,000 as a couple saves you no tax at all, because you were always going to take the $32,200 instead.
Bunching
Since the threshold is annual, deductions that are optional in timing can be concentrated into alternate years.
A couple with $24,000 of other itemised deductions and $12,000 of annual giving:
- Spread: $36,000 in each of two years. Both itemise, and the benefit over the standard deduction is $3,800 per year — $7,600 in total.
- Bunched: $48,000 in year one and $24,000 in year two. Year one itemises for a $15,800 benefit; year two takes the standard deduction. Total benefit $15,800.
Twice the deduction from identical giving. A donor-advised fund is the usual mechanism — you take the deduction when you fund it and distribute to charities on whatever schedule you like, so the charities see no difference in timing.
The same idea works for elective medical procedures and, where permitted, for prepaying property tax — though the SALT cap frequently blocks the second one.
What counts, and the limits on each
- State and local taxes — income or sales tax plus property tax, capped at $40,400 for 2026 and phasing down above $505,000 of MAGI to a $10,000 floor.
- Mortgage interest — on up to $750,000 of debt for loans taken after December 2017, or $1 million for older ones.
- Charitable giving — generally up to 60% of AGI for cash gifts, with different limits for appreciated assets.
- Medical expenses — only the part above 7.5% of AGI, which is why the field above asks for the excess rather than the total. On $100,000 of AGI the first $7,500 of medical spending is not deductible at all.
Why so few people itemise now
The standard deduction was roughly doubled in 2017 and the SALT deduction was capped at the same time. Between them, the share of filers who itemise fell sharply — from around a third to under a tenth. For most households the standard deduction now wins comfortably, which is why the bunching question only becomes interesting for people close to the line.
Figures are for tax year 2026 and change annually. This is arithmetic, not tax advice.
