Free calculators
Free calculators for small-business owners, home offices and people running AI on their own computers. Each one shows its formulas, links to the official sources behind its figures, and runs entirely in your browser: nothing you type is sent anywhere or stored, and there are no cookies, ads or trackers.
- 2026 Self-Employment Tax and Quarterly Estimate Calculator
Estimate 2026 self-employment tax (15.3% on 92.35% of profit, $184,500 wage base), income tax from the 2026 IRS rate schedules, and quarterly estimated payments under the 90%/100%/110% safe harbors. An estimate, not tax advice.
- UPS Battery Backup Calculator: Size (VA and Watts) and Runtime
Add up your equipment's watts, convert to VA with a power factor, size a UPS so it runs at no more than 80% of capacity, and get an idealized battery runtime estimate from volts and amp-hours. Formulas and manufacturer sources shown.
- 2026 Mileage Deduction Calculator (72.5¢ and 76¢ IRS Rates)
Work out a 2026 standard mileage deduction with both IRS business rates (72.5 cents a mile through June 30 and 76 cents from July 1), plus parking and tolls, and your business-use percentage. Medical and charity rates included.
- Local AI Model Memory Calculator (RAM and VRAM for GGUF Models)
Estimate how much RAM or VRAM a local AI model needs: parameters × bits per weight for the weights, plus the KV cache for your context length. Quantization sizes from Hugging Face and llama.cpp, the KV formula from NVIDIA, presets from official model configs.
- Missed-Call Cost Calculator for Small Businesses
Put a number on missed calls using your own figures: missed calls a week, how many callers you lose, how many would have become customers, and what a customer is worth. Also shows the break-even for an answering option. No built-in statistics.
- Home Office Deduction Calculator (IRS Simplified Method)
Figure the IRS simplified home office deduction: $5 per square foot, up to 300 square feet ($1,500), with Publication 587's monthly averaging for part-year use or a change in space, and the gross income limit. An estimate, not tax advice.
- Section 179 vs. Bonus Depreciation Calculator (2026 IRS Limits)
Compare the first-year write-off for business equipment under Section 179, 100% bonus depreciation and regular MACRS, using the 2026 IRS limits ($2,560,000; phase-out above $4,090,000; $32,000 heavy SUV cap), the business income limit and carryover. An estimate, not tax advice.
- Invoice Late Fee and Interest Calculator
Work out the interest and late fee on an overdue invoice from your own contract terms: simple daily interest (360- or 365-day year), monthly compounding using the U.S. Treasury's Prompt Payment formula, and a flat fee. No invented rates.
Calculators give estimates for general information, not tax, legal or professional advice. Each page lists its limits.