Billing & GST calculator

GST Calculator India

Add GST to a taxable price or extract GST from an inclusive bill, with CGST/SGST or IGST split, quantity, discount, invoice rounding, and optional margin checks.

Category: BusinessLast updated: 7 June 2026

Interactive calculator

Add GST or extract it from an inclusive price

Enter a per-unit amount. Quantity and discount are applied before GST is added or extracted.

Invoice amount and GST

Calculation mode Use Add GST for a pre-tax price. Use Extract GST when the entered price already includes GST. Amount per unit

Enter the price for one unit before quantity is applied. GST rate

Enter the rate that applies to the product or service. The field is not limited to preset rates. Transaction type Intra-state shows CGST and SGST. Inter-state shows IGST. Quantity

The amount is multiplied by quantity before discount and GST.

Quick rates:

These are convenient presets, not a complete official rate list. The GST rate field remains editable.

Discount, rounding, cost, and margin

Cost price is per unit. Enter both cost and target margin to compare the pre-GST selling value with your target.

Discount (optional)

Discount is applied to amount × quantity before GST is added or extracted. Round final invoice amount Choose Yes to round only the final customer payable amount to the nearest rupee. Cost price per unit (optional)

Optional product cost for checking pre-GST margin. It does not include other business expenses. Target profit margin (optional)

Optional target as a percentage of the pre-GST selling value. Enter cost price as well for a target comparison.

GST rates can change and vary by product/service. Check the official GST portal or a tax professional for compliance.

Add GST result

₹1,180.00

Final customer invoice

Exclusive

GST-inclusive amount entered: ₹1,000.00
Taxable/base amount: ₹1,000.00
Discount amount: ₹0.00
GST added: ₹180.00
CGST: ₹90.00
SGST: ₹90.00
IGST: ₹0.00
Base amount per unit: ₹1,000.00
Final amount per unit: ₹1,180.00
Invoice rounding adjustment: ₹0.00

What this means

GST is added on top of the taxable value. The pre-GST base is ₹1,000.00, GST is ₹180.00, and the customer total before invoice rounding is ₹1,180.00. For this intra-state sale, GST is split into CGST ₹90.00 and SGST ₹90.00.

Practical decision

Use the final invoice amount for the customer quote and the pre-GST base when checking revenue or margin.

What to try next

Compare this customer total with an inclusive quote or add cost and target margin to check price protection.

Check another rate, change, or margin in Percentage Calculator

Estimate only. This is for bill understanding and price planning, not GST return filing, tax advice, or a compliance guarantee.

What to do next

Continue your decision

Formula, example, assumptions, and FAQs — open any section for the detail.

Formula

Exclusive price: add GST

Discounted base = amount × quantity − discount · GST = discounted base × rate ÷ 100 · Invoice total = discounted base + GST

Use exclusive mode when GST is added on top of the quoted price. The discount reduces the taxable base before GST is calculated.

Inclusive price: extract GST

Inclusive total = amount × quantity − discount · Base = inclusive total ÷ (1 + rate ÷ 100) · GST inside price = inclusive total − base

Use inclusive mode when the bill or selling price already includes GST. This separates the customer total into its pre-GST value and tax portion.

CGST, SGST, and IGST split

Intra-state: CGST = GST ÷ 2 and SGST = GST ÷ 2 · Inter-state: IGST = full GST amount

The calculator shows the simple split selected by the user. Actual invoice treatment can depend on place of supply, registration, and the nature of the supply.

Optional price and margin check

Estimated margin = pre-GST base − total entered cost · Target base = total cost ÷ (1 − target margin ÷ 100)

Margin is checked against the pre-GST selling value because GST collected from the customer is not treated as profit. Other costs are not estimated.

Worked example

Example: ₹1,000 at 18% GST

A seller enters ₹1,000 for one unit, selects 18% GST, no discount, and an intra-state transaction.

Calculation:In Add GST mode, GST is ₹1,000 × 18% = ₹180, split as CGST ₹90 and SGST ₹90. The customer pays ₹1,180. If ₹1,000 were entered in Extract GST mode instead, base value would be ₹1,000 ÷ 1.18 = ₹847.46 and GST inside the price would be ₹152.54.

Result:Exclusive and inclusive modes answer different questions. Use ₹1,180 as the customer total when GST is added on top; use ₹847.46 as the pre-GST value when ₹1,000 already includes GST.

Assumptions

The entered amount and optional cost price are per-unit figures; quantity is applied before discount and GST.
Discount is a percentage of amount × quantity and is applied before GST is calculated or extracted.
In exclusive mode, the entered amount does not include GST. In inclusive mode, it already includes GST.
The user selects intra-state or inter-state treatment; the calculator does not determine place of supply.
CGST and SGST are split as evenly as possible to paise while keeping their sum equal to GST.
Optional margin uses pre-GST selling value and product cost only. Overheads, cess, delivery, marketplace fees, input tax credit, and other charges are excluded.
Final invoice rounding, when selected, changes only the customer payable total and is shown as a separate adjustment.

Common mistakes

Using Add GST when the entered bill amount already includes GST.
Using Extract GST when the quoted amount is actually before tax.
Applying the full GST rate to both CGST and SGST instead of splitting the selected total rate between them.
Treating GST collected from the customer as sales margin or profit.
Applying discount after GST when the intended taxable value should be reduced before tax.
Choosing intra-state or inter-state treatment without checking place-of-supply rules.
Assuming a common preset rate applies to every product or service.

Accuracy notes

Money values are calculated deterministically and displayed to paise. Small one-paise differences can appear when an odd GST amount is split between CGST and SGST. Actual invoices can differ because of line-level rounding, cess, fees, place-of-supply treatment, input tax credit, product classification, or rate changes.

Frequently asked questions

What is the difference between Add GST and Extract GST?

Add GST starts with a pre-tax amount and puts GST on top. Extract GST starts with a GST-inclusive customer price and separates it into the base amount and GST already inside it.

How are CGST and SGST different from IGST?

For a selected intra-state sale, this calculator divides GST into CGST and SGST. For a selected inter-state sale, it shows the full tax as IGST. Confirm the correct treatment for the actual supply.

Is discount applied before GST?

Yes. This calculator applies the entered discount to amount × quantity first. Exclusive mode calculates GST on that reduced base; inclusive mode extracts GST from the reduced inclusive total.

Can I enter a GST rate that is not in the quick buttons?

Yes. The GST rate field is editable. The quick buttons are only shortcuts and are not a complete official rate list.

Why is margin calculated before GST?

GST collected from the customer is generally a tax component, not product margin. The calculator therefore compares cost with the pre-GST base. It does not account for input tax credit or other business costs.

Can I use this result to file a GST return?

No. This calculator is for price planning and understanding a bill. It does not prepare returns, determine registration or place of supply, classify HSN/SAC, or guarantee compliance.

Estimate only, not tax or legal advice. Verify the applicable GST rate, product or service classification, registration position, place of supply, invoice treatment, and filing requirements through the official GST portal or a qualified tax professional.Read the full disclaimer.

Last updated: 7 June 2026More Business calculators