Free online calculators
Use free calculators for loans, mortgage refinancing, percentages, discounts, tips, sales tax, compound interest, GPA, BMR and exchange rates.
What can you do with these tools?
PocketKit calculators cover personal finance, purchases, study and health estimates. Each page explains its formula, units and limitations. Loan, tax, GPA and health results support comparison and planning but do not replace lender quotes, official transcripts, tax advice or medical guidance. Live exchange rates require a network connection; basic calculations generally run in the current browser.
Core tools
- Percentage Calculator — X% of Y, ratios and percent change
- Loan Calculator — Monthly payment, total interest and full amortization
- Mortgage Refinance Calculator — Compare your current mortgage with refinance options to find monthly savings, total interest saved, and the break-even period.
- Compound Interest Calculator — Compound growth with optional monthly contributions
- Sales Tax Calculator — US state sales tax, with tax-inclusive reverse mode
- Discount Calculator — Sale price and savings, with stacked discounts and tax
- GPA Calculator — Calculate overall and semester GPA with course grades, credits and various grading scales (4.0, 4.3, 5.0, WES).
- BMR & TDEE Calculator — Compute Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) with Mifflin-St Jeor & Harris-Benedict formulas.
Why calculator results can differ
| Task or input | Tool | Decision criteria and limits |
|---|---|---|
| Loans and interest | Loan Calculator | Rate, term, compounding and fees change results |
| Percentages and discounts | Percentage Calculator | Confirm base value, direction and rounding |
| GPA | GPA Calculator | Use the institution credit weights and grading scale |
| BMR | BMR & TDEE Calculator | Formula, age, weight and activity factor affect estimates |
Recommended workflow
- Normalize units and confirm the formula
- Keep unrounded intermediate results
- Cross-check institutional rules
More tools (2)
- Tip Calculator — Tip and total by rate, split across people
- Currency Converter — Convert 30+ currencies at live mid-market rates with edge caching and offline fallback — for global pricing and expenses
Frequently asked questions
Can results be used as formal financial or medical advice?
No. Results use your inputs and the formula stated on the page and are intended for estimation and comparison. Use authoritative records and professional advice for loans, taxes, grades or health decisions.
Why can results differ from a bank, school or another calculator?
Formulas, rounding, compounding frequency, included fees, grading rules and activity factors can differ. Compare the method shown on the page with the rules of the relevant institution.
Do calculators store entered values?
Basic calculations generally run in the current browser without sending inputs to the PocketKit API. Live exchange rates require a network request. Check each tool page for its specific data-handling label.