Casualty Loss Deduction Calculator

How a Casualty Loss Is Calculated

IRS Publication 547 figures a personal casualty loss in four steps.

1. Take the smaller of the drop in fair market value or your adjusted basis (generally what you paid plus improvements).
2. Subtract insurance and other reimbursements.
3. Subtract $100 per casualty.
4. Subtract 10% of your adjusted gross income from the total of the year’s federal casualty losses.

Real property you use personally (land, the house and its landscaping) is figured as one item. Furniture and other belongings are figured item by item and then added together.

Pub 547’s worked example. A hurricane damaged a home in a FEMA-designated area in September 2025.

• The home and land cost $134,000. Fair market value fell from $147,500 to $100,000, so the drop is $47,500. That is less than the basis, so $47,500 counts.
• Furniture, figured item by item, added $3,000, and nothing was insured. Total loss: $50,500.
• Subtract $100: $50,400. Subtract 10% of the $71,000 AGI ($7,100).
• The deduction is $43,300, which is the calculator’s default.

The 2025-2026 Rules: Declared Disasters, $100, 10% and $500

• Federally declared disaster: a major-disaster or emergency declaration by the President under the Stafford Act.
• Qualified disaster losses come from major disasters declared in 2016, Hurricanes Harvey, Irma and Maria, and, after P.L. 119-21, major disasters declared from January 1, 2020 through September 2, 2025 that meet the incident-period rules. Declarations made only because of COVID-19 do not count. IRS.gov/DisasterTaxRelief lists the dates.
• Standard deduction add-on: a net qualified disaster loss can be added to the standard deduction on Schedule A line 16 and Form 1040 line 12e. The standard deduction is $31,500 married filing jointly, $15,750 single and $23,625 head of household for 2025, and $32,200, $16,100 and $24,150 for 2026.
• Prior-year election: a loss in a FEMA-designated area can be deducted on the preceding year’s return. That can mean a faster refund, and it uses that year’s AGI.

Scenarios

Treated as a qualified disaster loss, the same hurricane damage gives $50,000 after the $500 reduction, with no AGI floor. A married couple who don’t itemize would claim $82,200 in total, the 2026 standard deduction plus the loss. Pub 547’s other example shows the 10% rule: two separate federally declared floods ($1,800 and $2,100) each lose $100, and 10% of a $25,000 AGI leaves a $1,200 deduction.

Common Mistakes

• Deducting a loss that is not from a declared disaster. A house fire, car accident or burglary is not deductible for personal property unless you also have casualty gains.
• Using replacement cost. The loss is the drop in value, capped at your basis, not what it costs to buy new.
• Forgetting to subtract insurance, including amounts you expect to receive. If you do not file a claim on insured property, the insured part is not deductible.
• Applying $100 per item. It is $100 per casualty event, however many items were damaged.
• Itemizing when it does not pay. A federal casualty loss only helps if total itemized deductions beat the standard deduction. Qualified disaster losses are the exception.

What This Calculator Does Not Cover

It handles one casualty event for personal-use property. It does not cover:

• Business or income-producing property.
• Casualty gains, or netting several events.
• Theft losses from scams entered into for profit.
• The Pub 547 safe harbors for valuing damage (repair cost, de minimis and others).
• Postponing gain when insurance exceeds basis.
• State tax rules.

Use Form 4684, and for a large loss, a prior-year election or a home that was a business or rental, work with a tax professional. IRS.gov/DisasterTaxRelief lists current declarations and deadline postponements.

Frequently Asked Questions

How to Use This Calculator

1. Pick what caused the loss — a federally declared disaster, a qualified disaster, or neither.
2. Enter basis and values — adjusted basis, and fair market value just before and after the event.
3. Add other items and insurance — belongings figured item by item, and any insurance or other reimbursement.
4. Enter AGI and filing status — AGI for the 10% rule; year and status for the qualified-disaster standard deduction add-on.