Result
How to use this calculator
Enter each deduction you can document: home office square footage, business miles driven, the business share of phone and internet, self-employed health insurance premiums, and retirement plan contributions. The calculator totals your business expenses and above-the-line adjustments, then estimates the tax they save at your marginal rate.
The formula
Business expenses (home office at $5/sq ft up to 300 sq ft, mileage at the IRS standard rate, phone/internet business share) reduce your net profit. Above-the-line items (half of SE tax, SE health insurance, retirement contributions) reduce your adjusted gross income. Estimated savings = total deductions × your marginal tax rate.
2025 reference rates
Standard mileage rate: 70 cents per mile (business). Home office simplified method: $5 per square foot, capped at 300 square feet. Verify both with the IRS each January — they change.