VAT / GST & Sales Tax Calculator
Calculate tax-exclusive and tax-inclusive amounts with exact decimal cent rounding, invoice field guidance and dated official rate references.
About this vat / gst & sales tax calculator
Calculate tax-exclusive and tax-inclusive amounts with exact decimal cent rounding, invoice field guidance and dated official rate references Computes exact algebraic and numerical metrics directly in your browser using IEEE 754 precision without round-trip latency.
Formula & calculation mechanics
The execution engine processes input tokens and applies transformations in the browser sandbox. Specifically, Let r be the percentage rate. Net input: tax = round(net × r / 100); gross = net + tax. Gross input: tax = round(gross × r / (100 + r)); net = gross − tax. Tax is rounded half up to two decimal places using exact decimal integer arithmetic; the input amount is preserved.
Worked numerical calculation
Scenario: Example: 120 including 20% tax
Sample input:
Processing: Let r be the percentage rate. Map net to the amount excluding tax, tax to the tax amount, and gross to the total payable. Confirm the applicable rate and the sum before entry. For example, 120.00 including 20% tax gives net 100.00, tax 20.00 and total 120.00. These are amount fields only, not a complete legal invoice; check required identifiers, dates, currency and your invoicing system’s rules.
Illustrative output:
Domain range & precision boundaries
One amount and one rate. No item-by-item or multiple-rate invoice, exemptions, reverse charge, tax credits, refunds or compounded taxes. Invoice systems can use different rounding and allocation rules. This is an arithmetic aid, not a tax-control-device validation or a guarantee against invoice rejection. Both fields are required. Use nonnegative decimals with a dot: amount 0–999999999999.99 (up to 2 decimal places), rate 0–100% (up to 4). Up to 64 characters per field; surrounding whitespace and leading zeros are accepted. No signs, exponents, commas or currency symbols.
Calculations in VAT / GST & Sales Tax Calculator use standard IEEE 754 precision or exact rational models. Verify significant accounting or tax figures with authoritative references.
In-browser calculation boundary
Formula calculations and numeric evaluations in VAT / GST & Sales Tax Calculator run synchronously in the browser JavaScript engine with zero server telemetry.
Mathematical formulas & precision standards
Mathematical constants, IEEE 754 floating-point standards, and numerical analysis specifications:
- Exact decimal tax arithmetic; tax rounded half up to cents; net + tax = gross
VAT / GST & Sales Tax Calculator verification · Audit standards
How to use it
- Both fields are required.
- Tax is rounded first, then the other amount is obtained by subtraction or addition, so net + tax always equals gross. At half-cent ties, rounding net independently can differ. A reverse calculation after rounding can differ by a cent. This model uses two decimal places, even for currencies with other minor units.
- Click the action button or observe immediate live calculations rendered by VAT / GST & Sales Tax Calculator.
Frequently asked questions
Calculation and rounding+
Operational requirements for "Calculation and rounding" are verified in local memory during execution of VAT / GST & Sales Tax Calculator.
Invoice amount fields+
Boundary constraints concerning "Invoice amount fields" prevent invalid parameter state mutations client-side.
Country and region rates+
Official references checked on 2026-10-03; this is a dated snapshot, not a live tax service. Standard rates do not apply to every transaction. China’s 13%, 9% and 6% categories are distinct, not interchangeable; the law took effect on 2026-01-01. Check the linked rules for scope, reduced or zero rates and exemptions before using a rate.
Input amount type+
Both fields are required.