Free tool

GST calculator

Add GST to an amount or strip it back out, and get the CGST, SGST and IGST figures exactly as they need to appear on the invoice.

Amount (₹)

GST rate

Taxable value: ₹10,000.00
CGST @ 9%: ₹900.00
SGST @ 9%: ₹900.00
Total: ₹11,800.00

Calculated in your browser — nothing is sent to a server. Cess, composition rates and special-category cases are not covered.

How is GST calculated?

Adding GST (exclusive)

GST = amount × rate ÷ 100

The amount you start with is the taxable value, and the tax goes on top. This is the normal case when you are pricing your own work.

Removing GST (inclusive)

base = total ÷ (1 + rate ÷ 100)

Use this when a price already contains GST — a retail tag, or a quote agreed as “all inclusive”.

Worked example: ₹10,000 at 18%

The total is the same in both cases. Only the split — and which lines appear on the invoice — changes.

Line	Same state	Other state
Taxable value	₹10,000.00	₹10,000.00
CGST @ 9%	₹900.00	—
SGST @ 9%	₹900.00	—
IGST @ 18%	—	₹1,800.00
Total	₹11,800.00	₹11,800.00

Read the other way: a GST-inclusive total of ₹11,800 at 18% divides by 1.18 to give ₹10,000 of taxable value and ₹1,800 of tax. Subtracting 18% of ₹11,800 would give ₹9,676 — which is the arithmetic that quietly under-reports a taxable value.

Which rate applies to what you sell?

GST is levied in slabs, and the slab follows the HSN code for goods or the SAC code for services rather than the broad category a product feels like it belongs to. Two similar-sounding items can sit in different slabs, so it is worth looking up rather than assuming.

We do not reproduce the rate list here on purpose. Rates change by notification, and a stale rate table on a tax page is worse than none — check the current rate on the official GST portal, which publishes the authoritative rate finder.

GST on a real invoice

A calculator handles one line. An invoice usually has several, and a few things behave differently once there is more than one:

Multiple rates.Tax is computed per line at that line’s own rate, then summed — not on the invoice total at a blended rate.
Discounts. A discount shown on the invoice and agreed at or before the time of supply reduces the taxable value. One given afterwards does not.
The split follows the place of supply, which is decided by the state codes in the two GSTINs — see the GST state code list for how that comparison works.
The total in words is a mandatory field on a tax invoice, and it is the one people most often leave off.

Doing this per line, per invoice, by hand is the actual work. ईnvocify applies the right rate per line from the HSN or SAC code, decides the CGST/SGST or IGST split from the place of supply, and writes the total in words — then sends it on WhatsApp with a UPI link attached.

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Frequently asked questions

How do you remove GST from a total that already includes it?: Divide the total by (1 + rate/100). At 18%, a GST-inclusive total of ₹11,800 divides by 1.18 to give a taxable value of ₹10,000, so the GST is ₹1,800. Subtracting 18% of the total instead is the common mistake — that would give ₹9,676, which is wrong.
When do I charge CGST and SGST instead of IGST?: When the supply is intra-state — your state and your customer’s place of supply are the same. The total tax is identical either way; only the split changes. At 18% intra-state you charge 9% CGST plus 9% SGST, and inter-state you charge 18% IGST as a single line.
Which GST rate applies to what I sell?: The rate follows the HSN code for goods or the SAC code for services. Look yours up on the official rate finder on the GST portal rather than assuming — the same broad category can span more than one slab.
Is GST calculated on the price before or after a discount?: On the discounted value, provided the discount is shown on the invoice and was agreed at or before the time of supply. A discount given later, without having been agreed up front, does not reduce the taxable value.
Does this calculator handle cess?: No. Compensation cess applies to a small set of goods such as tobacco, aerated drinks and some motor vehicles, and it is charged in addition to GST at item-specific rates. Add it separately.

How is GST calculated?

Adding GST (exclusive)

GST = amount × rate ÷ 100

The amount you start with is the taxable value, and the tax goes on top. This is the normal case when you are pricing your own work.

Removing GST (inclusive)

base = total ÷ (1 + rate ÷ 100)

Use this when a price already contains GST — a retail tag, or a quote agreed as “all inclusive”.

Worked example: ₹10,000 at 18%

The total is the same in both cases. Only the split — and which lines appear on the invoice — changes.

Line	Same state	Other state
Taxable value	₹10,000.00	₹10,000.00
CGST @ 9%	₹900.00	—
SGST @ 9%	₹900.00	—
IGST @ 18%	—	₹1,800.00
Total	₹11,800.00	₹11,800.00

Which rate applies to what you sell?

GST on a real invoice

A calculator handles one line. An invoice usually has several, and a few things behave differently once there is more than one:

Multiple rates.Tax is computed per line at that line’s own rate, then summed — not on the invoice total at a blended rate.

Discounts. A discount shown on the invoice and agreed at or before the time of supply reduces the taxable value. One given afterwards does not.

The split follows the place of supply, which is decided by the state codes in the two GSTINs — see the GST state code list for how that comparison works.

The total in words is a mandatory field on a tax invoice, and it is the one people most often leave off.

Start a free 7-day trial

Frequently asked questions

How do you remove GST from a total that already includes it?

Divide the total by (1 + rate/100). At 18%, a GST-inclusive total of ₹11,800 divides by 1.18 to give a taxable value of ₹10,000, so the GST is ₹1,800. Subtracting 18% of the total instead is the common mistake — that would give ₹9,676, which is wrong.

When do I charge CGST and SGST instead of IGST?

When the supply is intra-state — your state and your customer’s place of supply are the same. The total tax is identical either way; only the split changes. At 18% intra-state you charge 9% CGST plus 9% SGST, and inter-state you charge 18% IGST as a single line.

Which GST rate applies to what I sell?

The rate follows the HSN code for goods or the SAC code for services. Look yours up on the official rate finder on the GST portal rather than assuming — the same broad category can span more than one slab.

Is GST calculated on the price before or after a discount?

On the discounted value, provided the discount is shown on the invoice and was agreed at or before the time of supply. A discount given later, without having been agreed up front, does not reduce the taxable value.

Does this calculator handle cess?

No. Compensation cess applies to a small set of goods such as tobacco, aerated drinks and some motor vehicles, and it is charged in addition to GST at item-specific rates. Add it separately.