GST CalculatorGST Calculator

GST Calculator

Calculate Goods and Services Tax (GST) online: add GST to an exclusive base price or remove GST from a GST-inclusive total. Pick a 5%–28% rate preset or enter any rate for an instant base, CGST/SGST split and total breakdown.

Use the currency shown on your quote, receipt, or invoice.

15% is only the starting value. Replace it with the rate that applies to your transaction.

Calculation Mode
Base Amount100.00
GST (15%)+ 15.00
CGST / SGST / IGST SplitIGST (15%): 15.00
CGST (7.5%)7.50
SGST (7.5%)7.50
TOTALTotal Amount
115.00

Your total is 1.15× the amount before GST. Use this total for a GST-added quote or invoice.

Need 9% GST plus service charge? Singapore GST calculator

GST Inclusive vs. GST Exclusive Calculator: Should You Add or Remove GST?

Start with the price you already have. A pre-tax quote or invoice line starts before tax (GST exclusive); a retail receipt or displayed price already includes tax (GST inclusive). Choosing the wrong direction produces the wrong GST component — even when you enter the right percentage. - Price before GST (Ex GST): Choose Add GST to calculate the tax and final price with GST. - Price with GST included: Choose Split GST from total to remove GST and recover the pre-tax base. - Instant breakup: View the base amount, total GST, 50/50 CGST + SGST intra-state split, and final total together.

How to use the GST Calculator

1

Enter the amount

Type the price before GST, or the final total that already includes it.

2

Set rate and direction

Enter the GST rate, then choose Add GST or Split GST from total to match that starting figure.

3

Check the breakdown

Read base, GST and total. Copy if you need the figures elsewhere.

How to Calculate Goods and Services Tax (GST) Online for Invoices & Bills

Goods and Services Tax (GST) is a value-added tax levied on goods and services. When preparing a tax invoice or checking a bill online, select the GST percentage that applies to your supply and let the calculator compute the net price and tax breakup: - 5%, 12%, 18%, 28% (India GST slabs): Standard GST rates where intra-state invoices split equally into CGST (Central GST) and SGST (State GST) — for example, 18% GST = 9% CGST + 9% SGST — while inter-state supplies charge IGST. - 5% (Canada Federal GST): Federal Goods and Services Tax before provincial HST, PST, or QST. - 9% (Singapore GST): Standard IRAS GST rate on goods, services, and restaurant bills. - 10% (Australia GST): Standard ATO rate where GST equals 1/11th of a GST-inclusive price. - 15% (New Zealand GST): Standard Inland Revenue rate where inclusive prices multiply by 3 and divide by 23.

GST Calculation Formula & CGST / SGST Split Explained

The GST formula depends on whether your starting figure is GST exclusive (before tax) or GST inclusive (tax already included). 1. Add GST Formula (GST Exclusive) - GST Amount = Base Price × (GST Rate ÷ 100) - Gross Total = Base Price + GST Amount 2. Remove GST Formula (GST Inclusive) - Base Price = Inclusive Total ÷ (1 + GST Rate ÷ 100) - GST Component = Inclusive Total − Base Price 3. CGST, SGST & IGST Split Formula - Intra-state (CGST + SGST): CGST = SGST = Total GST ÷ 2 (each at half the GST rate) - Inter-state (IGST): IGST = Total GST (at the full GST rate) Worked 18% & 10% Examples: Adding 18% GST to 1,000 gives 180 GST (90 CGST at 9% + 90 SGST at 9%) and a 1,180 total. To remove 18% GST from 1,180, divide by 1.18 to recover 1,000 — never subtract 18% directly. At 10% GST, $200 before tax adds $20 GST for a $220 total, and $220 ÷ 1.10 recovers $200.

Worked Examples: Adding GST to a Quote vs. Splitting GST from a Receipt

Compare forward (GST exclusive) and reverse (GST inclusive) calculations side by side, including how 10% and 18% GST rates split on invoices.

Generic worked examples, not customer results.

Quote before GST: add 10% to $200.00

A generic service quote starts with a price before GST.

Input: $200.00 before GST at one 10% GST rate.

Output: GST = $20.00; total = $220.00.

Why: GST is 10% of the before-tax amount ($200.00 × 10% = $20.00). On an 18% invoice of 1,000.00, GST is 180.00 (90.00 CGST at 9% + 90.00 SGST at 9%) for a 1,180.00 total.

Use: Use this breakdown when preparing a quote or invoice that starts before GST.

Boundary: This arithmetic assumes one rate applies to the whole amount; calculate mixed-rate lines separately.

Rule: start before GST, multiply by the rate, then add the tax.

Receipt total includes GST: split $220.00 at 10%

A generic receipt or displayed price already includes GST.

Input: $220.00 total at one 10% GST rate.

Output: Before GST = $200.00; GST = $20.00.

Why: Divide $220.00 by 1.10 (or divide 1,180.00 by 1.18 at 18% GST) to reverse the tax increase. Subtracting 10% directly gives $198.00, which understates the original base price.

Use: Use this split to check a receipt or a GST-inclusive displayed price.

Boundary: This arithmetic assumes one rate applies to the whole amount; check each mixed-rate line separately.

Rule: start with a GST-inclusive total, divide by one plus the rate, then subtract to find GST.

Common GST Percentage Calculation Mistakes to Avoid

Three arithmetic errors account for most invoice and receipt discrepancies: - Subtracting a percentage from an inclusive total: Never subtract the GST rate directly from a tax-inclusive bill. Taking 15% off $115 gives $97.75 instead of dividing by 1.15 to get the true $100 base. - Doubling CGST and SGST instead of splitting: On an 18% intra-state invoice, CGST is 9% and SGST is 9% of the same base amount — they split the 18% tax in half rather than adding 18% twice. - Mixing tax slabs or rounding too early: Calculate each GST rate slab (such as 5%, 12%, and 18% items) on separate invoice lines before summing, and keep unrounded figures until the final two-decimal invoice total. Use Add GST above when quoting from a pre-tax price, Split GST from total for a quick receipt check, the Reverse GST Calculator for downloadable backwards breakdowns, or the ITC Calculator to offset IGST, CGST, and SGST input tax credits.

GST Calculator FAQ

Q1.How do I add GST to a price?

Multiply the base price by the GST rate divided by 100 to find the GST, then add it to the base price. For example, $100 at 10% GST gives $10 GST and a $110 total.

Q2.How do I remove GST from a total?

Divide the GST-inclusive total by 1 plus the GST rate as a decimal. At 10%, divide by 1.10. The result is the base price; subtract it from the total to find the GST component.

Q3.Why can’t I subtract the GST percentage directly?

GST is calculated from the base price, not the final total. Directly subtracting the percentage from a GST-inclusive total gives the wrong base. Use division, or open the Reverse GST Calculator for the complete backwards-calculation workflow.

Q4.Which GST rate should I choose (5%, 9%, 10%, 12%, 15%, 18%, or 28%)?

Select the preset that matches your jurisdiction and tax slab, or type any custom percentage: 5%, 12%, 18%, and 28% cover India's GST slabs (and 5% is Canada's federal GST), 9% applies in Singapore, 10% in Australia, and 15% in New Zealand. Always verify the rate on your tax invoice.

Q5.How are CGST, SGST, and IGST calculated on GST Exclusive vs. GST Inclusive prices?

First find the total GST: add GST to a GST-exclusive base price, or divide a GST-inclusive total by (1 + rate ÷ 100) to extract GST. For intra-state supplies, CGST and SGST each equal half of the GST rate and half of the GST amount (for example, 18% GST splits into 9% CGST + 9% SGST). For inter-state supplies, IGST equals 100% of the GST amount.

Q6.How does the calculator handle decimals and currencies?

It keeps unrounded values during calculation and displays two decimal places. All results use the same currency as the amount you enter; no currency conversion occurs. Follow the source invoice and local rules for final rounding.

Q7.Does this calculator file or pay GST for me?

No. It performs the arithmetic for one GST rate at a time. Check the original transaction's rate, rounding, exemptions, invoice requirements and filing rules before relying on it for a return.

Q8.Are my amounts stored or sent to a server?

No. The calculation runs in your browser, and this homepage calculator does not store your amounts on a server.

Disclaimer: This tool provides arithmetic for one GST rate at a time, not tax, legal or filing advice. Check the original transaction's rate, rounding, exemptions, invoice requirements and filing rules before using a result for an invoice or return.