GST Calculator

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Add or remove GST at 5%, 12%, 18% or 28% with CGST/SGST/IGST split, reverse GST from an inclusive price and GST hidden inside an MRP.

Inputs

What do you want to do?

Amount / MRP (₹)

Net price for “add”, invoice or MRP value for the other two modes

GST rate

Type of supply

Quantity

Units on the invoice line

How to use this calculator: GST Calculator

Add or remove GST at 5%, 12%, 18% or 28% with CGST/SGST/IGST split, reverse GST from an inclusive price and GST hidden inside an MRP. The example below is calculated by this page's real engine from the displayed inputs.

1Confirm that the GST Calculator matches the quantity or design check you need.
2Enter Amount / MRP and Quantity using the units printed beside each field.
3Select the applicable What do you want to do?, GST rate, and Type of supply options; these choices change the calculation method or factors.
4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.

Input guide and example values

Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.

Input	Example value	Why it matters
What do you want to do?	Add GST — amount is exclusive (net price)	Select the option that matches the real installation or scenario.
Amount / MRP	10000 ₹	Net price for “add”, invoice or MRP value for the other two modes
GST rate	18% — standard rate (most services)	Select the option that matches the real installation or scenario.
Type of supply	Intra-state — same state (CGST + SGST)	Select the option that matches the real installation or scenario.
Quantity	1	Units on the invoice line

Formula, derivation and worked example

GST is a destination-based value-added tax charged on the taxable value, not on the price you see on the shelf. When a price already includes tax — an MRP, a restaurant bill, a cab fare — you must work backwards with Net = Price × 100 / (100 + rate). Simply taking 18% of an inclusive ₹1,180 gives ₹212.40, which is wrong; the correct GST is ₹180 and the net value is ₹1,000. For supply inside one state the levy splits equally into CGST (Centre) and SGST (State); for supply across states a single IGST at the same total rate applies. MRP in India is legally the maximum price inclusive of all taxes, so any GST inside an MRP is always a reverse calculation.

Add GST: GST = Net × rate / 100 ; Invoice = Net + GST

Reverse GST: Net = Inclusive × 100 / (100 + rate) ; GST = Inclusive − Net

GST on MRP: Selling price = MRP × (1 − discount/100) ; Net = SP × 100 / (100 + rate)

Intra-state: CGST = SGST = GST / 2

Inter-state: IGST = GST

Shortcut: GST fraction of an inclusive price = rate / (100 + rate)

Substitution steps

1. Taxable value
amount entered (exclusive)
= ₹10,000.00
2. GST
10,000.00 × 18.00 / 100
= ₹1,800.00
3. CGST / SGST each
GST / 2
= ₹900.00
4. Invoice total
10,000.00 + 1,800.00
= ₹11,800.00

Computed example results

Invoice total (incl. GST): ₹11,800.00
Total GST: ₹1,800.00; 18.00% CGST + SGST
CGST: ₹900.00; 9.00%
SGST / UTGST: ₹900.00; 9.00%
Taxable value: ₹10,000.00
Invoice total: ₹11,800.00

Understanding the result

Read the main result together with supporting checks, assumptions, limits and intermediate values.

For a manual check, repeat the first equation, confirm the units and change one input at a time.

Common mistakes when using GST Calculator

Do not mix units for Amount / MRP (₹). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
Do not leave What do you want to do? on the default choice unless that choice matches the real scenario; the selected option can change the calculation path or factor.
Do not replace the displayed Add GST: GST = Net × rate / 100 ; Invoice = Net + GST relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
Do not treat Invoice total (incl. GST) = ₹11,800.00 from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.

When the GST Calculator is useful

GST Calculator is designed for cases where What do you want to do?, Amount / MRP, GST rate, Type of supply are known and you need Invoice total (incl. GST), Total GST, CGST. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.

Use the calculator for the scope described by its inputs and notes. The displayed method is Add GST: GST = Net × rate / 100 ; Invoice = Net + GST. If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.

What do you want to do? and Amount / MRP: what changes the answer

The worked example uses What do you want to do? = Add GST — amount is exclusive (net price), Amount / MRP = 10000 ₹, GST rate = 18% — standard rate (most services), Type of supply = Intra-state — same state (CGST + SGST). With those values, Invoice total (incl. GST) is ₹11,800.00. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.

For this calculator, the main input roles are: What do you want to do?: Select the option that matches the real installation or scenario. Available choices include Add GST — amount is exclusive (net price), Remove GST (reverse) — amount already includes GST, GST inside an MRP — with optional discount. Amount / MRP (₹): Net price for “add”, invoice or MRP value for the other two modes GST rate: Select the option that matches the real installation or scenario. Available choices include 0% — exempt (fresh milk, bread, books), 0.25% — rough diamonds, 3% — gold, silver, jewellery, 5% — essentials, economy items. Type of supply: Select the option that matches the real installation or scenario. Available choices include Intra-state — same state (CGST + SGST), Inter-state — different state (IGST).

How to sanity-check a GST Calculator result

Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Invoice total (incl. GST), because it is the first worked-example output shown by the live engine.

Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.

Next logical calculator

Continue with Percentage Calculator

Percentage Calculator is directly connected from GST Calculator as a source-defined continuation or comparison.

Open Percentage Calculator

Standards, source trail and limitations

References show the method used. Check the current local edition, amendments and project specification before a regulated decision.

Formula

Add GST: GST = Net × rate / 100 ; Invoice = Net + GST
Reverse GST: Net = Inclusive × 100 / (100 + rate) ; GST = Inclusive − Net
GST on MRP: Selling price = MRP × (1 − discount/100) ; Net = SP × 100 / (100 + rate)
Intra-state: CGST = SGST = GST / 2
Inter-state: IGST = GST
Shortcut: GST fraction of an inclusive price = rate / (100 + rate)

Engineering notes

Intra-state supply (same state) → CGST + SGST. Inter-state supply, exports and imports → IGST.
The buyer's total is identical under both routes; only the split between Centre and State changes.
Compensation cess on tobacco, aerated drinks and larger vehicles is charged over and above 28% and is not included here.

GST slabs, splits and inclusive fractions

Multiply an inclusive price by the last column to get the GST inside it.

Slab	CGST	SGST/UTGST	IGST	Typical supplies	GST inside an inclusive price
0%	0%	0%	0%	Fresh milk, bread, unbranded grain, printed books	0%
0.25%	0.125%	0.125%	0.25%	Rough diamonds and precious stones	0.249%
3%	1.5%	1.5%	3%	Gold, silver, jewellery	2.913%
5%	2.5%	2.5%	5%	Packaged food, economy transport, small restaurants	4.762%
12%	6%	6%	12%	Processed food, mobile phones, business-class air travel	10.714%
18%	9%	9%	18%	Most goods and services, IT, telecom, AC restaurants (5% without ITC)	15.254%
28%	14%	14%	28%	Cars, ACs, aerated drinks, tobacco (plus cess)	21.875%

Formulas explained

GST = Net × rate / 100

Forward calculation used on a tax invoice, where the quoted price is exclusive of tax.

Net: Taxable value of the supply, after any trade discount
rate: Applicable slab: 0, 0.25, 3, 5, 12, 18 or 28%

Net = Inclusive × 100 / (100 + rate)

Reverse (backward) GST. Taking rate% of an inclusive price overstates the tax — at 18% it inflates GST by about 18%.

Inclusive: Price already containing GST — MRP, bill total, cab fare

Equivalent one-step form: GST = Inclusive × rate / (100 + rate).

CGST = SGST = GST / 2 · IGST = GST

Intra-state supply splits equally between Centre and State; inter-state supply is a single IGST at the same total rate, so the buyer pays the same either way.

CGST: Central GST, half the slab for intra-state supply
SGST/UTGST: State or Union Territory GST, the other half
IGST: Integrated GST on inter-state supply and imports

Add GST vs reverse GST

Add GST when your price is a net or ex-GST quote — multiply by the rate. Reverse GST when the figure already includes tax — divide by (100 + rate) and multiply by 100. Choosing the wrong direction at 18% changes the tax by roughly 15%.

Why GST on MRP is always reverse

Under the Legal Metrology (Packaged Commodities) Rules, MRP is the maximum retail price inclusive of all taxes. A seller cannot add GST on top of MRP; the tax already sits inside it, so it must be extracted with the reverse formula.

The inclusive-fraction shortcut

The GST inside any inclusive price is rate / (100 + rate): 4.762% at 5%, 10.714% at 12%, 15.254% at 18% and 21.875% at 28%. Multiply the bill by that fraction to get the tax in one step.

Discounts and taxable value

A discount shown on the invoice and agreed before supply reduces the taxable value, so GST is charged on the discounted price. Post-sale discounts only qualify if they were pre-agreed and linked to the original invoice.

Worked example

1Add GST: ₹10,000 net at 18% → GST ₹1,800 (CGST ₹900 + SGST ₹900), invoice ₹11,800.
2Reverse GST: ₹11,800 inclusive at 18% → net ₹10,000 and GST ₹1,800 (11,800 × 100 / 118).
3GST inside an MRP: MRP ₹1,499 at 18% with 10% discount → selling price ₹1,349.10, net ₹1,143.31, GST ₹205.79.

Assumptions

Rate applies to the entire taxable value — no composite or mixed supply split.
Compensation cess on demerit goods (over and above 28%) is not included.
Input tax credit is not netted off; this is the gross tax on one supply.
Discount is a pre-invoice trade discount, so it reduces the taxable value.

Tips

Reverse GST in one step: GST = Inclusive × rate / (100 + rate). At 18% that is 18/118 = 15.254% of the bill.
A tax invoice for intra-state supply must show CGST and SGST on separate lines; IGST appears as a single line.
Check the HSN/SAC code before assuming a slab — many goods sit at 5% or 12%, not 18%.
Post-sale discounts only reduce GST if they were agreed before supply and are linked to the invoice.

Warnings

Compensation cess applies above 28% on tobacco, aerated drinks and some vehicles.
Wrong place-of-supply classification (IGST vs CGST + SGST) triggers interest and re-payment.
Charging above MRP, even to recover GST, is an offence under the Legal Metrology Act.

Standards & references

CGST Act 2017
SGST Acts 2017
IGST Act 2017
GST Council rate schedules
Legal Metrology (Packaged Commodities) Rules 2011

Frequently asked questions

How do I calculate reverse GST?

Divide the inclusive price by (100 + rate) and multiply by 100. For ₹5,000 inclusive of 18%: 5000 × 100 / 118 = ₹4,237.29 net and ₹762.71 GST.

What is the GST formula?

Adding GST: GST = Amount × rate ÷ 100. Removing GST: GST = Amount × rate ÷ (100 + rate). Total = taxable value + GST.

Is GST charged on MRP?

No. MRP is already the maximum retail price inclusive of all taxes, so GST is extracted from it, never added on top. Use the “GST inside an MRP” mode.

How is GST split into CGST and SGST?

For supply within the same state the total rate splits equally — 18% becomes 9% CGST + 9% SGST. Across states the whole 18% is charged as IGST.

How much GST is in a ₹100 item at 18%?

If ₹100 is exclusive, GST is ₹18 and the total is ₹118. If ₹100 already includes GST, the net value is ₹84.75 and the GST is ₹15.25.

Which GST slab applies to my product?

Look up the HSN code in the GST Council rate schedule. Essentials are 0% or 5%, processed goods 12%, most goods and services 18%, and luxury or sin goods 28% plus cess.

What inputs does the GST Calculator use?

It uses What do you want to do?, Amount / MRP, GST rate, Type of supply, and Quantity. Follow the unit printed for each field and choose any selectable option to match the real scenario.

What does the GST Calculator calculate?

It calculates Invoice total (incl. GST), Total GST, CGST, SGST / UTGST, Taxable value, and Invoice total. With the displayed default inputs, Invoice total (incl. GST) is ₹11,800.00.

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