GST Calculator – Add or Remove GST

What is the GST Calculator?

The FinanceDeck GST Calculator handles both directions of the Goods and Services Tax computation: adding GST to a net (pre-tax) amount to get the gross invoice value, and reverse-calculating the GST component and net amount from a gross figure. It supports all four standard Indian GST slabs — 5%, 12%, 18% and 28%.

Whether you're a freelancer raising an invoice, a small business owner reconciling books, or a customer verifying a bill, this tool eliminates the mental math and prevents rounding errors that add up over dozens of transactions.

How does it work?

In 'add' mode, the calculator multiplies your net amount by the chosen GST rate to get the tax and adds it back for the gross. In 'remove' mode, it uses the reverse formula Net = Gross ÷ (1 + rate/100) so you can extract exactly what the tax component is inside a tax-inclusive invoice.

Every result updates live as you change amount, rate or mode — no page reload, no submit button. That makes it ideal for quickly running through a whole batch of invoices side by side.

Formula

Add: GST = Net × rate/100; Remove: Net = Gross ÷ (1 + rate/100)

Example

You want to raise an invoice for ₹10,000 worth of services at 18% GST. Adding GST gives ₹1,800 tax and a gross invoice value of ₹11,800.

Conversely, if a client's PO says the total is ₹11,800 GST-inclusive, the reverse mode extracts ₹1,800 as GST and ₹10,000 as your taxable value — the number you actually recognise as revenue.

Benefits

✓Handles both add-GST and extract-GST scenarios
✓Covers all four Indian GST slabs — 5, 12, 18, 28%
✓Perfect for freelancers, SMEs and accountants
✓Avoids rounding mistakes on bulk invoices
✓Instant result — no login, no ads, no data stored

Frequently Asked Questions

Which GST rate should I use?

It depends on the HSN/SAC code of the good or service. Most professional services are 18%, essential goods 5%, and luxury items 28%. Check the official GST rate finder if unsure.