Tax Deduction Calculator
A single filer earning $75,000 who claims a $20,000 itemized deduction instead of the $15,400 standard deduction cuts taxable income by an extra $4,600 – saving roughly $1,012 at a 22% marginal rate. Knowing which route delivers the bigger break is the core problem a tax deduction calculator solves.
What Is a Tax Deduction?
A tax deduction is an expense the IRS allows you to subtract from your gross income, producing a lower figure called adjusted gross income (AGI) or taxable income. Because federal income tax is calculated on taxable income, every dollar you deduct saves you your marginal tax rate percentage in actual tax.
Two broad categories exist:
- Above-the-line deductions – available to all filers regardless of whether they itemize (e.g., student loan interest, educator expenses, IRA contributions).
- Below-the-line deductions – claimed as either the standard deduction or a total of itemized deductions, whichever is larger.
How Does the Tax Deduction Calculator Work?
The calculator compares two scenarios for your filing status and income:
- Standard deduction path – applies the fixed IRS amount for 2026.
- Itemized deduction path – totals your mortgage interest, state and local taxes (SALT), charitable contributions, medical expenses above the 7.5%-of-AGI threshold, and other qualifying costs.
It then multiplies the winning deduction amount by your marginal tax rate to show estimated tax savings. If your total itemized deductions fall below the standard deduction, the calculator flags that itemizing would cost you money.
2026 Standard Deduction Amounts
The IRS adjusts the standard deduction annually for inflation. Projected 2026 figures are:
| Filing Status | Standard Deduction |
|---|---|
| Single | $15,400 |
| Married Filing Jointly | $30,800 |
| Married Filing Separately | $15,400 |
| Head of Household | $23,100 |
An additional $1,650** (single/head of household) or **$1,350 (married) is added per taxpayer aged 65 or older or legally blind.
Verify the final amounts on IRS.gov when the official revenue procedure is published.
Which Expenses Can You Itemize?
Itemizing only makes sense when the total exceeds your standard deduction. The main categories:
- Mortgage interest – on up to $750,000 of acquisition debt for loans originated after December 15, 2017.
- State and local taxes (SALT) – income or sales tax plus property tax, capped at $10,000 ($5,000 for married filing separately).
- Charitable contributions – cash gifts up to 60% of AGI to qualifying organizations; non-cash donations at fair market value.
- Medical and dental expenses – only the portion exceeding 7.5% of your AGI.
- Casualty and theft losses – only in federally declared disaster areas.
- Other itemized deductions – certain investment interest, unreimbursed employee business expenses in specific cases.
How to Calculate Your Tax Savings From a Deduction
The formula is straightforward:
Tax savings = Deduction amount × Marginal tax rate
2026 Federal Income Tax Brackets (Projected, Single Filers)
| Tax Rate | Taxable Income Range |
|---|---|
| 10% | $0 – $11,925 |
| 12% | $11,926 – $48,475 |
| 22% | $48,476 – $103,350 |
| 24% | $103,351 – $197,300 |
| 32% | $197,301 – $250,525 |
| 35% | $250,526 – $626,350 |
| 37% | Over $626,350 |
Worked Example
Sarah is single with a $90,000 salary. Her itemized deductions total $18,500:
| Item | Amount |
|---|---|
| Mortgage interest | $9,200 |
| SALT (capped) | $10,000 |
| Charitable donations | $2,800 |
| Medical expenses (above 7.5% AGI) | $0 |
| Total itemized | $18,500 |
Her standard deduction would be **$15,400**. Itemizing saves an extra $3,100 in taxable income.
Sarah’s marginal rate is 22% (income falls in the $48,476–$103,350 bracket).
Extra tax savings from itemizing = $3,100 × 22% = **$682**.
If Sarah’s only deductions were $9,200 in mortgage interest and $3,000 in charitable gifts ($12,200 total), the standard deduction would win and she should not itemize.
Above-the-Line Deductions Worth Knowing
These reduce AGI directly, regardless of whether you take the standard deduction:
- Educator expenses – up to $300 per teacher.
- Student loan interest – up to $2,500 (phases out at higher incomes).
- IRA contributions – up to $7,000 ($8,000 if age 50+), subject to income limits.
- HSA contributions – up to $4,300 (self-only) or $8,550 (family) for 2026.
- Self-employment tax deduction – 50% of SE tax paid.
- Alimony – for agreements finalized before January 1, 2019.
Lowering AGI can unlock eligibility for other credits and deductions that have AGI-based phase-outs.
Standard vs. Itemized: Quick Decision Guide
| Situation | Likely Better Option |
|---|---|
| You rent, have no large charitable gifts | Standard deduction |
| You own a home with a sizable mortgage | Run the numbers – may favor itemizing |
| SALT + mortgage interest alone exceed standard deduction | Itemize |
| You had major medical bills (>7.5% AGI) | Itemize |
| You made large charitable donations | Itemize |
| You have few or no qualifying expenses | Standard deduction |
When in doubt, total your itemized deductions and compare against the standard deduction for your filing status. The tax deduction calculator above handles this comparison instantly.
Common Mistakes to Avoid
- Forgetting the SALT cap – listing the full amount of state income tax and property tax without applying the $10,000 ceiling inflates your total incorrectly.
- Mixing personal and deductible expenses – only interest on your primary and secondary residence qualifies; credit card interest does not.
- Ignoring above-the-line deductions – even if you take the standard deduction, you can still claim educator expenses, student loan interest, and HSA contributions.
- Not bunching deductions – if your itemized total is close to the standard deduction, concentrating charitable gifts or medical procedures into a single year can push you over the threshold every other year.
This article provides general information, not personalized tax advice. Consult a qualified tax professional or refer to IRS Publication 17 for guidance specific to your situation.