How Much is GST? Rates and Calculators Explained

Whether you’re running a small business or just trying to figure out a receipt, GST (and its cousins VAT and HST) can sneak up on you. The math isn’t complicated, but the rates vary wildly depending on where you are — and that’s where most people get stuck. This guide walks you through the actual numbers for Australia, India, and Ireland, with formulas you can use right now.

Australia GST rate: 10% · New Zealand GST rate: 15% · Ireland VAT rate: 23% · India GST slabs: 0%, 5%, 12%, 18%, 28% · UK VAT standard rate: 20%

How much GST is in $100?

Working out GST on a round number is easier than most people expect — once you know the formula. For Australia at 10%, the math breaks down to two quick steps.

Australia example

A $100 invoice before GST becomes $110 total. The GST component is $9.09, which you can verify by reversing the calculation: $110 ÷ 1.1 = $100 base, then $110 − $100 = $9.09 GST.

Other countries

In Ireland at 23% VAT, the same $100 base becomes $123 total, with $23 in VAT. India uses slabs — $100 at 18% gives $18 GST (total $118), while the same $100 at 28% adds $28 (total $128). The pattern holds: multiply by (1 + rate), then subtract the base to isolate the tax.

Is GST 10 or 11 percent in Australia?

Australia’s GST is 10%. There is no 11% rate and never has been. The Australian Government explicitly states that “GST is a broad-based tax of 10% on most goods, services and other items sold” (Moneysmart.gov.au (ASIC consumer finance portal)).

Current rate

Since July 1, 2000, when Australia replaced its wholesale sales tax with GST, the rate has held steady at 10% (Enterslice (tax consultancy)). No legislation to change it has passed as of 2026.

Historical changes

The rate was set at 10% at implementation and has not moved. This makes Australia’s GST one of the most stable consumption taxes globally — compare that to countries with variable VAT rates tied to economic conditions or EU directives.

Australia’s single-rate approach provides predictability that businesses and consumers can rely on without needing to track changing tax bands.

What is the GST rate in Ireland?

Ireland calls its consumption tax VAT (Value-Added Tax), but the function is identical to GST. The standard rate is 23%, which is among the highest in the EU (CountryTaxCalc (VAT reference tool)).

Standard VAT

Ireland’s 23% standard rate applies to most goods and services. Businesses must register for VAT once turnover hits €80,000 for goods or €40,000 for services (CountryTaxCalc (VAT reference tool)). This is higher than Australia’s GST registration threshold of $75,000.

Reduced rates

Ireland operates multiple VAT bands — 13.5% for hospitality and building services, 9% for certain cultural events and sports facilities, and 4.8% for newspapers and e-books (CountryTaxCalc (VAT reference tool)). This complexity contrasts sharply with Australia’s single 10% rate.

The catch: businesses operating across multiple sectors in Ireland must track which VAT rate applies to each transaction type, adding compliance complexity compared to single-rate systems.

How do I calculate GST?

The core calculation is the same across most GST/VAT systems: apply the rate to the pre-tax amount. Here’s how to do it correctly in each country.

Including GST

To get the total from a pre-tax price: multiply by (1 + rate). For Australia at 10%: $200 × 1.1 = $220. For Ireland at 23%: €200 × 1.23 = €246. For India at 18%: ₹200 × 1.18 = ₹236.

Excluding GST

To strip GST from a gross amount: divide by (1 + rate). Australia: $220 ÷ 1.1 = $200. Ireland: €246 ÷ 1.23 = €200. India at 18%: ₹236 ÷ 1.18 = ₹200.

Excel formula

In Excel, put your pre-tax amount in cell A1. Enter the GST rate as a decimal in B1 (0.10 for Australia). Then:

• GST amount: =A1*B1
• Total including GST: =A1*(1+B1)
• Reverse GST from total in C1: =C1/(1+B1) then GST = C1−C1/(1+B1)

These formulas work for any country — just swap the rate decimal for Ireland (0.23), India (0.18), or any other GST/VAT system.

What is the current GST rate?

“Current” depends entirely on which country you’re in. Here’s how the major systems stack up heading into 2026.

India slabs

India uses a multi-tier slab system: 0%, 5%, 12%, 18%, and 28% on most goods and services, with additional cess on luxury items (ClearTax (India tax platform)). India’s highest slab of 28% is among the steepest globally (Wise (international payments platform)). The exact applicable slab depends on the specific product or service category.

Global variations

Australia, New Zealand, and Singapore each apply a single rate: 10%, 15%, and 9% respectively. This makes them easier to calculate than India’s tiered approach (Commenda (GST structure comparison)). Canada operates differently: a 5% federal GST plus provincial HST ranging from 13% to 15% depending on province.

The implication: businesses operating internationally must maintain separate calculation logic for each country’s tax structure rather than applying a universal formula.

How to Calculate GST: Step-by-Step

Follow these steps to calculate GST or VAT for any country with a single rate like Australia, New Zealand, or Ireland’s standard band.

1. Identify the rate: Find the current GST/VAT rate for your country (10% Australia, 15% NZ, 23% Ireland standard).
2. Determine if you owe it: Check the registration threshold — Australian businesses register when turnover exceeds A$75,000 (Tax, Super + You (Australian Government)).
3. Calculate the GST component: Multiply the pre-tax amount by the decimal rate (e.g., $200 × 0.10 = $20 GST).
4. Add to get the gross: $200 + $20 = $220 total. Or use the multiplier: $200 × 1.1 = $220.
5. Verify with an official calculator: Use Moneysmart.gov.au (Australian Government consumer portal) for Australia or Wise (international payments platform) for India.

The pattern: once you know the rate, the math stays consistent across any pre-tax amount — making automation straightforward for businesses handling recurring calculations.

GST vs VAT: The Structural Differences

GST and VAT are the same tax concept under different names. The real variation is in how countries implement them.

Single-rate vs multi-tier

Australia applies 10% uniformly to most goods and services, with specific exemptions for fresh food, medical services, and some educational supplies (CountryTaxCalc (2026 VAT reference)). India uses slabs — the same product category always gets the same rate, but rates range from 0% on essential goods up to 28% on luxury items (Wise (India GST calculator)).

Exemptions vs reduced rates

Australia exempts certain essentials from GST entirely. Ireland instead uses reduced VAT rates (13.5%, 9%, 4.8%) for specific sectors rather than full exemptions (CountryTaxCalc (2026 VAT reference)). India’s approach is the broadest — different product categories carry different slabs.

What this means: businesses in single-rate countries like Australia enjoy simpler compliance, while multi-tier systems require product classification expertise that varies by jurisdiction.

Registration Thresholds Across Countries

Knowing when you must register for GST or VAT is as important as knowing the rate itself.

GST is a broad-based tax of 10% on most goods, services and other items sold.

Moneysmart.gov.au (ASIC consumer finance portal)

For every $100 worth of goods or services you purchase in Australia, you will have to pay an additional $10 in GST.

SmartGSTCalc (GST calculation tool)

For Australian businesses, the $75,000 registration threshold is the real decision point — below it, you don’t charge GST; above it, you must register and remit. Ireland’s multiple VAT bands add complexity that single-rate countries like Australia avoid entirely. India’s tiered system requires knowing your product category before you can even begin calculating.

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