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GST Calculator

Add or remove GST with preset GST rates or a custom rate, and see original amount, GST amount, final amount, formula, and steps.

  • tax
  • goods and services tax
  • inclusive gst
  • exclusive gst

Enter the taxable amount for GST exclusive calculations or the GST-inclusive amount for reverse GST.

Use this only when Custom rate is selected.

Status: initial

Results

Awaiting calculation

Explore your result

Invoice tax breakup

Explore the gst calculator result visually while keeping this page's detailed guidance and examples.

ā‚¹1,180.00Total

Invoice tax breakup

Original amount
ā‚¹1,000.00
GST
ā‚¹180.00

Use this result well

  1. 1Verify the calculator inputs.
  2. 2Compare the key result relationships.
  3. 3Review the page guidance before acting.

Confirm whether CGST and SGST or IGST applies to the invoice.

Calculator guide

Introduction

The GST Calculator adds GST to a base amount or removes GST from an inclusive total. It also shows taxable value, GST amount, invoice total, CGST/SGST split, IGST amount, reverse-GST factor, and an invoice-style summary.

What is a GST calculator?

Use this calculator to quickly check GST arithmetic for Indian invoices, quotes, product prices, service fees, and reverse-GST totals. It supports common GST slabs, special rates, the higher 40% slab, and a custom rate.

GST formula

For GST-exclusive amounts, GST is added to the taxable value. For GST-inclusive amounts, reverse GST is found by dividing the total by 1 plus the GST rate. Intra-state tax is commonly split into CGST and SGST/UTGST, while inter-state tax is shown as IGST.

Variable explanations

Understand what each input and result means before calculating.

Amount

The entered amount is either before GST for exclusive calculations or already including GST for inclusive calculations.

GST rate

Choose a common rate such as 0%, 0.25%, 3%, 5%, 12%, 18%, 28%, 40%, or select a custom rate.

Calculation type

GST Exclusive adds GST to a base amount. GST Inclusive removes GST from a total amount.

CGST

Central GST, commonly shown as half of total GST for intra-state transactions.

SGST/UTGST

State GST or Union Territory GST, commonly shown as the other half of total GST for intra-state transactions.

IGST

Integrated GST, commonly used for inter-state transactions.

Taxable value

The pre-GST amount used for invoice and tax calculations.

Reviewed by the Calculator.org.in Editorial Team

Formula behavior, validation cases, explanatory examples, and cited sources are checked before publication. This review supports educational accuracy and is not a substitute for qualified professional advice.

Last reviewed: 2026-08-03

Review process

Formula guide

See the calculation logic, variable definitions, and practical meaning.

GST Exclusive (add GST)

GST amount = original amount x GST rate / 100

  • Original amount is the price before GST.
  • GST rate is the selected percentage.
  • Final amount is original amount plus GST amount.

Use this when the entered amount does not include GST and you want the GST-inclusive invoice total.

GST Inclusive (remove GST)

Original amount = GST-inclusive amount / (1 + GST rate / 100)

  • GST-inclusive amount is the total price including GST.
  • GST rate is converted to a decimal.
  • GST amount is total amount minus original amount.

Use this when the entered amount already includes GST and you want to find the taxable value.

CGST and SGST split

CGST = GST / 2 and SGST = GST / 2

  • Used for many intra-state transactions.
  • UTGST may apply in union territories.

The total GST amount is split equally between central and state or union territory heads.

IGST amount

IGST = full GST amount

  • Used for many inter-state transactions.

The full GST amount is shown under IGST instead of splitting into CGST and SGST.

Final amount

Final amount = original amount + GST amount

  • Final amount is the invoice or bill total after GST is applied.

For inclusive calculations, the entered amount is already the final amount.

Reverse GST factor

Reverse factor = 1 + GST rate / 100

  • Divide an inclusive total by this factor.

This explains why reverse GST is not calculated by simply subtracting the GST percentage.

Custom GST rate

Custom rate follows the same exclusive or inclusive formulas

  • Custom rate can be any value from 0% to 100%.

Use a custom rate for item-specific rates, special cases, or GST/VAT-style checks.

Worked examples

Follow realistic inputs through the calculation step by step.

1

Worked example

Add 18% GST

  1. 1Choose GST Exclusive.
  2. 2Enter amount as 1,000.
  3. 3Choose 18%.
  4. 4GST is 180 and the final amount is 1,180.
2

Worked example

Remove 18% GST

  1. 1Choose GST Inclusive.
  2. 2Enter amount as 1,180.
  3. 3Choose 18%.
  4. 4Original amount is 1,000 and GST is 180.
3

Worked example

Intra-state split

  1. 1If GST amount is 180, CGST is 90 and SGST is 90.
  2. 2Use this view for invoice checks where CGST and SGST are shown separately.
4

Worked example

Inter-state IGST

  1. 1If GST amount is 180, IGST is 180.
  2. 2Use this view when the transaction is reported as IGST instead of CGST plus SGST.
5

Worked example

40% GST check

  1. 1Choose GST Exclusive.
  2. 2Enter the taxable value.
  3. 3Choose 40%.
  4. 4Use this for higher-slab what-if or invoice arithmetic checks where applicable.
6

Worked example

Invoice check

  1. 1Use GST Inclusive when checking a total invoice amount.
  2. 2Enter the total amount shown on the invoice.
  3. 3The calculator separates taxable value, GST amount, and invoice total.

Common mistakes

Avoid these common input and interpretation errors.

Confusing inclusive and exclusive amounts

Adding GST to an amount that already includes GST will overstate the final price.

Using the wrong rate

GST rates vary by goods, services, HSN/SAC classification, transaction date, and official notifications. Always confirm the applicable rate.

Subtracting the rate directly

To remove GST from an inclusive amount, divide by 1 plus the rate. Do not simply subtract the percentage from the total.

Mixing CGST/SGST and IGST

The same total GST amount may be reported differently depending on whether the transaction is intra-state or inter-state.

Ignoring current versus legacy slabs

Some older invoices and references use 12% or 28%, while newer references may use simplified slabs such as 0%, 5%, 18%, and 40%.

Rounding too early

Round final invoice values consistently and avoid rounding each intermediate step when checking larger invoices.

Treating estimates as tax advice

A calculator can help with arithmetic, but filing and compliance questions should follow official guidance.

Frequently asked questions

Quick answers to the questions users ask most often.

What is GST?
GST stands for Goods and Services Tax. It is a tax applied to many goods and services depending on the applicable rules and rate.
What is GST exclusive?
GST exclusive means the entered amount does not include GST. The calculator adds GST to find the final amount.
What is GST inclusive?
GST inclusive means the entered amount already includes GST. The calculator removes GST to find the original amount.
How do I add GST?
Multiply the original amount by the GST rate divided by 100, then add that GST amount to the original amount.
How do I remove GST from a total?
Divide the GST-inclusive amount by 1 plus the GST rate divided by 100. Subtract that original amount from the total to find GST.
What GST rates are supported?
The calculator supports 0%, 0.25%, 3%, 5%, 12%, 18%, 28%, 40%, and a custom rate from 0% to 100%.
What is CGST?
CGST is Central Goods and Services Tax, commonly part of an intra-state GST split.
What is SGST or UTGST?
SGST is State Goods and Services Tax and UTGST is Union Territory Goods and Services Tax, commonly paired with CGST for intra-state transactions.
What is IGST?
IGST is Integrated Goods and Services Tax, commonly used for inter-state transactions.
Does this calculator split CGST and SGST?
Yes. It shows CGST and SGST/UTGST as an equal split of the total GST amount, plus the full IGST amount for inter-state reference.
Can I use decimals?
Yes. Amounts support decimal values up to two decimal places, and custom GST rates can use decimals.
What is the formula for GST exclusive calculation?
GST amount equals original amount multiplied by GST rate divided by 100. Final amount equals original amount plus GST amount.
What is the formula for GST inclusive calculation?
Original amount equals GST-inclusive amount divided by 1 plus GST rate divided by 100. GST amount equals total minus original amount.
Why is reverse GST not just subtracting the percentage?
The percentage is applied to the original pre-GST value, not the GST-inclusive total, so reverse GST requires division.
Does 0% GST work?
Yes. A 0% rate leaves the original amount and final amount the same, with GST amount shown as zero.
What is a custom GST rate for?
Use a custom rate when checking a rate not listed in the preset options or when working with another GST/VAT-style rate.
Can businesses use this for invoices?
It can help check arithmetic for invoices and quotes, but official invoices should follow the applicable tax rules and accounting process.
Does this tell me the correct HSN or SAC rate?
No. It calculates GST arithmetic after you select a rate. Confirm item classification from official sources or your tax professional.
Why do some sources mention 12% and 28% while others mention 40%?
GST slabs and item classifications can change. Use the rate that applies to the transaction date and item category you are checking.
Are formulas calculated in the page component?
No. The page renders a registered calculator specification and the Formula Engine performs the calculation.
Does this replace tax advice?
No. It is an arithmetic tool, not legal, accounting, or tax filing advice.

References

Sources used to support the calculator guidance.

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Version history

A transparent record of calculator content updates.

Updated 2026-08-03
  • 1.1.0 Ā· 2026-08-03

    Added CGST/SGST/IGST breakdowns, invoice summary, rate reference, reverse factor, 0.25% and 40% preset rates, table steps, and expanded India GST guidance.

  • 1.0.0 Ā· 2026-07-03

    Initial CAL-0004 GST Calculator implementation using platform engines.