GST Calculator

What is a GST calculator?

A GST calculator splits any price into its net value, the Goods and Services Tax, and the GST-inclusive total for whatever rate you enter. It works in two directions: it can add GST to a tax-exclusive (net) price, or remove GST from a tax-inclusive (gross) price to reveal the underlying amount and the tax inside it.

GST is a broad value-added tax charged on most goods and services. India runs it as a multi-slab system (5%, 12%, 18%, 28%), while countries such as Australia, Singapore and New Zealand apply a single national rate. This tool handles all of them — just type in the correct rate.

How is GST calculated?

To add GST to a net price, the calculator uses two steps:

• GST = amount × rate ÷ 100
• Gross = amount + GST

To remove GST from a gross (inclusive) price, it works backwards:

• Net = amount ÷ (1 + rate ÷ 100)
• GST = amount − net

The “Add GST” mode treats your amount as the net (pre-tax) figure; the “Remove GST” mode treats it as the gross (tax-included) figure. Results are rounded to two decimal places.

Worked example: adding GST (exclusive price)

A supplier quotes a product at a net 2,000 and needs to add 18% GST.

1. GST = 2,000 × 18 ÷ 100 = 360
2. Gross = 2,000 + 360 = 2,360

So the customer pays 2,360, of which 360 is tax. If the rate were 5% instead, GST = 2,000 × 5 ÷ 100 = 100 and the gross would be 2,100.

Worked example: removing GST (inclusive price)

A retail receipt shows a GST-inclusive total of 1,180 and you want the net price and the tax at 18%.

1. Net = 1,180 ÷ (1 + 18 ÷ 100) = 1,180 ÷ 1.18 = 1,000
2. GST = 1,180 − 1,000 = 180

The product cost 1,000 before tax and the GST portion is 180. A handy shortcut: for an inclusive price, GST = gross × rate ÷ (100 + rate). Here that is 1,180 × 18 ÷ 118 = 180, which matches.

What are the India GST slabs?

India’s standard GST slabs are 0%, 5%, 12%, 18% and 28%. The table below shows the GST and gross total each slab produces on a net amount of 1,000, so you can sanity-check the calculator.

GST slab	Typical items	GST on 1,000	Gross (incl. GST)
0% (exempt)	Fresh produce, milk, books	0	1,000
5%	Essentials, transport, small restaurants	50	1,050
12%	Processed food, business-class air travel	120	1,120
18%	Most goods, electronics, services	180	1,180
28%	Cars, tobacco, aerated drinks, luxury	280	1,280

For intra-state sales these amounts are usually split equally into CGST and SGST (so 18% = 9% + 9%), while inter-state sales charge the whole figure as IGST.

When should you use inclusive vs exclusive mode?

Use the right mode or your numbers will be off by the tax amount:

• Add GST (exclusive): your listed price is before tax — common in B2B quotes and tax invoices where GST is shown as a separate line.
• Remove GST (inclusive): your price already includes tax — common in retail tags, receipts and consumer-facing MRP, where you need to extract the GST for accounting or input-tax credit.

A frequent mistake is treating an MRP (which already includes GST) as a net price and adding tax again — that double-counts the GST and inflates the total.

Real-world use cases

• Invoicing: sellers add GST to net quotes to bill customers correctly and show the tax line.
• Input tax credit: businesses remove GST from inclusive purchase totals to claim the credit they are owed.
• Pricing decisions: compare how each slab changes the shelf price before setting an MRP.
• Expense reconciliation: extract the tax from receipts when filing returns.

For more money tools, see the tax calculators category. If you are checking a tax refund or reverse calculation, the reverse sales tax calculator strips an embedded sales tax the same way, and the percentage calculator is handy for one-off rate maths.

Tips and common mistakes

• Match the mode to the price. Inclusive prices use “Remove”; exclusive prices use “Add”.
• Use the correct slab. Applying 18% to a 5% item over-charges the customer and risks compliance issues.
• Don’t round mid-calculation. Round only the final figures, as this calculator does, to avoid drift on large invoices.
• Include all taxable charges. Freight and handling are usually part of the taxable value, so add them to the net before computing GST.

Limitations and accuracy notes

This tool performs the standard add/remove GST arithmetic and rounds to two decimals; tiny differences from an invoice line may appear because of rounding rules or because composite supplies, reverse-charge entries or exemptions apply. It does not split CGST/SGST/IGST automatically, nor does it determine which slab a specific HSN/SAC code falls under. GST rates and classifications change — confirm the current rate for your country and product, and consult a qualified tax professional or your local tax authority before filing returns or issuing official invoices. This page is for general information only and is not tax advice.