Sales Tax / GST Calculator
Calculate tax amount and total price including sales tax, GST or VAT
Interactive Sandbox
Adjust values in real-time and observe mathematical cause-and-effect
Exponential Compounding Growth: Returns generate subsequent returns over time t, rapidly accelerating capital growth.
Variable Mechanics
Roles, constraints & impacts
Amount Before Tax
Formula Parameter
Tax Rate
Formula Parameter
At a Glance
Gotchas, units & real-world use
Formula Nature & Mechanics
Exponential Compounding Growth: Returns generate subsequent returns over time t, rapidly accelerating capital growth.
Common Mistakes & Traps
- Entering annual percentage rate (e.g. 7%) as 7 instead of converting to decimal 0.07.
- Neglecting the compounding frequency (n): monthly compounding produces higher yield than annual.
- Ignoring inflation drag when evaluating long-term nominal returns.
Dimensional Analysis & Units
Currency × (1 + rate)^time = Future Currency ($)
Real-World & Industry Application
Retirement 401(k) / Roth IRA compounding, mortgage amortization schedules, bond yield analysis, and inflation depreciation modeling.
Worked Example: Sales Tax / GST
Given:
- amount = 1000
- rate = 18
- Tax = 1000 × 18 / 100 = $180
- Total = 1000 + 180
- Total = $1,180
Answer: 1180
Frequently Asked Questions
What is the Sales Tax / GST formula?
Total = Amount + (Amount × Rate / 100). Calculate tax amount and total price including sales tax, GST or VAT.
How do I calculate Sales Tax / GST?
Enter Amount Before Tax (amount), Tax Rate (rate) into the calculator. It applies Total = Amount + (Amount × Rate / 100) and shows every step of the working.
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