GST Formula Explained (5%, 12%, 18%, 28%) in India – Calculate & Remove GST from Total Amount Easily
Whether you're a business owner, shopkeeper, accountant, freelancer, student, or online seller, understanding the GST formula can save time and prevent costly calculation mistakes. Many people struggle with questions like "How do I calculate 18% GST?", "How do I remove GST from a total amount?", or "What is the GST formula for 5%, 12%, 18%, and 28%?".
This guide explains every GST formula used in India with simple examples. You'll learn how to:
- Calculate GST on any amount
- Add GST to a price
- Remove GST from a GST-inclusive amount
- Understand formulas for 5%, 12%, 18%, and 28% GST
- Avoid common GST calculation mistakes
If you don't want to calculate manually, you can instantly calculate GST using our GST Calculator.
Quick Answer: GST Formula in India
To Add GST
GST Amount = Original Price × GST Rate ÷ 100
Final Price = Original Price + GST Amount
To Remove GST
Original Price = GST Inclusive Price ÷ (1 + GST Rate ÷ 100)
GST Amount = Inclusive Price − Original Price
These formulas work for every GST slab including 5%, 12%, 18%, and 28%.
What is GST?
GST (Goods and Services Tax) is a destination-based indirect tax introduced in India to replace multiple state and central taxes. Instead of paying VAT, Service Tax, Excise Duty, and several other indirect taxes separately, businesses now collect GST at a single applicable rate.
The tax collected is generally classified as:
- CGST (Central GST)
- SGST (State GST)
- IGST (Integrated GST)
Although GST has different components, the calculation formula remains exactly the same. Whether you're calculating CGST + SGST or IGST, you always begin with the same GST formula.
GST Formula Explained
The GST formula simply calculates a percentage of the original selling price. The GST percentage depends on the product or service category prescribed under Indian GST law.
Formula to Calculate GST
GST Amount = Original Price × GST Rate ÷ 100
Final Price = Original Price + GST Amount
This is the most commonly used GST formula across invoices, billing software, accounting systems, ERP solutions, POS systems, and e-commerce platforms.
GST Formula for Different GST Rates
| GST Rate | Formula |
|---|---|
| 5% | GST = Price × 5 ÷ 100 |
| 12% | GST = Price × 12 ÷ 100 |
| 18% | GST = Price × 18 ÷ 100 |
| 28% | GST = Price × 28 ÷ 100 |
The calculation process remains identical regardless of the GST slab. Only the GST percentage changes.
GST Formula with Examples
Example 1: 5% GST
Suppose the product price is ₹2,000.
GST = ₹2,000 × 5 ÷ 100 = ₹100
Final Price = ₹2,100
Example 2: 12% GST
Product Price = ₹5,000
GST = ₹5,000 × 12 ÷ 100 = ₹600
Final Price = ₹5,600
Example 3: 18% GST
Original Price = ₹10,000
GST = ₹10,000 × 18 ÷ 100 = ₹1,800
Invoice Amount = ₹11,800
Example 4: 28% GST
Original Price = ₹25,000
GST = ₹25,000 × 28 ÷ 100 = ₹7,000
Final Amount = ₹32,000
Calculate GST Instantly
Manual GST calculations are useful for understanding the formula, but they can become time-consuming when preparing invoices or checking multiple amounts.
Use our free GST Calculator to instantly:
- Add GST to any amount
- Remove GST from a GST-inclusive total
- Calculate GST for 5%, 12%, 18%, and 28%
- Split CGST and SGST automatically
- View accurate calculations in seconds
The calculator works for businesses, retailers, wholesalers, freelancers, accountants, students, and GST learners across India.
How to Remove GST from Total Amount
One of the most searched GST questions in India is:
- How to remove GST from total amount?
- Remove GST calculator
- How to remove 5 GST from total amount?
- GST inclusive formula
If you already have a GST-inclusive amount and want to find the original price before GST, a different formula is used.
In the next section, we'll explain the GST removal formula with step-by-step examples for 5%, 12%, 18%, and 28% GST.
How to Remove GST from Total Amount
Sometimes the amount you have already includes GST, such as an invoice total, online purchase amount, restaurant bill, or supplier quotation. In such cases, you need to calculate the original price before GST and determine the GST amount separately.
This process is commonly known as:
- Remove GST from total amount
- Reverse GST calculation
- GST exclusive calculation
- GST inclusive formula
Instead of subtracting the GST percentage directly from the total amount, you must use the correct GST removal formula.
GST Removal Formula
Original Price = GST Inclusive Amount ÷ (1 + GST Rate ÷ 100)
GST Amount = Inclusive Amount − Original Price
This formula works for every GST slab, including 5%, 12%, 18%, and 28%.
How to Remove 5% GST from Total Amount
Suppose the invoice amount is ₹2,100, including 5% GST.
Original Price = ₹2,100 ÷ 1.05 = ₹2,000
GST = ₹2,100 − ₹2,000 = ₹100
| Description | Amount |
|---|---|
| GST Inclusive Amount | ₹2,100 |
| Original Price | ₹2,000 |
| GST Amount | ₹100 |
How to Remove 12% GST from Total Amount
Suppose the invoice amount is ₹5,600.
Original Price = ₹5,600 ÷ 1.12 = ₹5,000
GST = ₹600
| Description | Amount |
|---|---|
| GST Inclusive Amount | ₹5,600 |
| Original Price | ₹5,000 |
| GST Amount | ₹600 |
How to Remove 18% GST from Total Amount
Suppose the invoice amount is ₹11,800.
Original Price = ₹11,800 ÷ 1.18 = ₹10,000
GST = ₹1,800
| Description | Amount |
|---|---|
| GST Inclusive Amount | ₹11,800 |
| Original Price | ₹10,000 |
| GST Amount | ₹1,800 |
How to Remove 28% GST from Total Amount
Suppose the invoice total is ₹32,000.
Original Price = ₹32,000 ÷ 1.28 = ₹25,000
GST = ₹7,000
| Description | Amount |
|---|---|
| GST Inclusive Amount | ₹32,000 |
| Original Price | ₹25,000 |
| GST Amount | ₹7,000 |
Need to Remove GST Instantly?
Instead of manually applying the GST removal formula every time, use our free GST Calculator to instantly calculate:
- Original amount before GST
- GST amount
- Final invoice value
- CGST and SGST split
- IGST calculations
Whether you're calculating GST for invoices, purchase bills, quotations, or online sales, the calculator provides accurate results in seconds.
GST Formula Table (5%, 12%, 18%, 28%)
| GST Rate | Multiplier for Adding GST | Divisor for Removing GST |
|---|---|---|
| 5% | × 1.05 | ÷ 1.05 |
| 12% | × 1.12 | ÷ 1.12 |
| 18% | × 1.18 | ÷ 1.18 |
| 28% | × 1.28 | ÷ 1.28 |
Many accounting software applications internally use these multipliers when calculating GST-inclusive and GST-exclusive prices.
Common GST Calculation Mistakes
1. Subtracting GST Percentage Directly
A common misconception is that you can remove GST by subtracting 18% from the total amount. This is incorrect because GST is already included in the total. You must divide by the appropriate multiplier (such as 1.18 for 18% GST) to arrive at the original price.
2. Using the Wrong GST Rate
Different goods and services attract different GST rates. Before calculating GST, confirm whether the applicable rate is 5%, 12%, 18%, or 28%.
3. Forgetting CGST and SGST Split
For intra-state transactions, the GST amount is generally divided equally into CGST and SGST. For example, 18% GST is usually split into 9% CGST and 9% SGST.
4. Rounding Too Early
Always perform the full calculation before rounding to two decimal places. Premature rounding can lead to small differences in invoice totals.
Where is the GST Formula Used?
The GST formula is used across a wide range of business and accounting activities in India, including:
- Retail billing and invoicing
- GST return preparation
- POS software and billing systems
- E-commerce marketplaces
- Supplier quotations
- Purchase and sales accounting
- Restaurant and café billing
- Freelance and professional service invoices
Understanding the GST formula helps businesses verify invoices, avoid pricing errors, and maintain accurate financial records.
Calculate GST Without Memorizing Formulas
While learning the GST formula is useful, manually calculating GST for every invoice isn't practical. Our free GST Calculator performs both GST addition and GST removal instantly for all major GST rates used in India.
Simply enter the amount, choose the GST rate, and receive accurate GST-exclusive and GST-inclusive values within seconds.
Frequently Asked Questions
The following section answers the most common GST formula questions asked by business owners, students, accountants, retailers, and taxpayers in India.
Frequently Asked Questions (FAQs)
What is the GST formula?
The GST formula is used to calculate Goods and Services Tax on a product or service. The basic formula is:
GST Amount = Original Price × GST Rate ÷ 100
The final invoice amount is calculated by adding the GST amount to the original price.
How do I calculate 18% GST?
Multiply the original price by 18 and divide by 100.
Example:
Original Price = ₹10,000
GST = ₹10,000 × 18 ÷ 100 = ₹1,800
Final Price = ₹11,800.
How do I remove GST from the total amount?
To remove GST from a GST-inclusive amount, divide the total amount by the GST multiplier.
For example, if GST is 18%:
Original Price = Inclusive Amount ÷ 1.18
GST Amount = Inclusive Amount − Original Price
How do I remove 5% GST from the total amount?
Divide the GST-inclusive amount by 1.05 to find the original price.
For example:
₹2,100 ÷ 1.05 = ₹2,000
GST = ₹100.
What is the GST formula for 12%?
GST = Original Price × 12 ÷ 100.
Final Price = Original Price + GST.
What is the GST formula for 28%?
GST = Original Price × 28 ÷ 100.
To remove 28% GST, divide the inclusive amount by 1.28.
Can I subtract GST directly from the total amount?
No. GST is already included in the total amount, so subtracting the GST percentage directly gives an incorrect result. Always use the GST removal formula by dividing the total amount by the GST multiplier.
How is GST calculated in India?
GST is calculated by multiplying the taxable value by the applicable GST rate. Depending on the transaction, the GST collected may be split into CGST and SGST or charged as IGST.
What are the current GST rates in India?
The most commonly used GST rates are 5%, 12%, 18%, and 28%. Some goods are exempt from GST or taxed at 0%, while selected items may have additional cess.
What is the formula for GST-inclusive price?
GST Inclusive Price = Original Price × (1 + GST Rate ÷ 100)
For example:
₹1,000 with 18% GST becomes ₹1,180.
What is the formula for GST-exclusive price?
GST Exclusive Price = GST Inclusive Amount ÷ (1 + GST Rate ÷ 100)
This formula helps determine the original amount before GST.
How do I calculate GST on an invoice?
Identify the taxable amount, apply the correct GST rate, calculate the GST amount, and add it to the taxable value. Most businesses use billing software or a GST calculator to automate this process.
How is 18% GST divided?
For intra-state transactions, 18% GST is generally divided into:
- 9% CGST
- 9% SGST
For inter-state transactions, the full 18% is charged as IGST.
What is the easiest way to calculate GST?
The easiest method is to use an online GST calculator. Simply enter the amount, select the GST rate, and the calculator instantly shows the GST amount, original price, and final invoice value.
You can use our GST Calculator to calculate GST in seconds.
Does the GST formula work for all GST rates?
Yes. The same formula works for every GST slab. Only the GST percentage changes, whether it is 5%, 12%, 18%, or 28%.
Can businesses use the GST formula for billing?
Yes. Businesses across India use the GST formula for invoices, quotations, POS billing, accounting software, GST return preparation, and tax compliance.
How do restaurants calculate GST?
Restaurants calculate GST by applying the applicable GST rate to the taxable value of food and beverages. The exact rate depends on the restaurant category and prevailing GST rules.
Can I calculate GST in Excel?
Yes. You can use formulas such as:
= A1 * 18 / 100
to calculate 18% GST, where A1 contains the original amount.
Is the GST formula different for services?
No. The GST calculation formula remains the same for both goods and services. Only the applicable GST rate varies depending on the nature of the supply.
Where can I calculate GST online for free?
You can use our free GST Calculator to calculate GST, remove GST from a total amount, split CGST and SGST, and calculate GST for 5%, 12%, 18%, and 28% instantly.
Ready to Calculate GST?
Whether you're preparing invoices, checking supplier quotations, verifying online purchase prices, or learning GST calculations, our free GST Calculator helps you perform accurate calculations in seconds.
Use the GST Calculator to:
- Add GST to any amount
- Remove GST from GST-inclusive prices
- Calculate 5%, 12%, 18%, and 28% GST
- Split CGST and SGST automatically
- Generate accurate values for billing and accounting
Final Thoughts
Understanding the GST formula is essential for businesses, accountants, retailers, freelancers, students, and taxpayers across India. Once you know how to calculate and remove GST correctly, preparing invoices and verifying bills becomes much easier.
Instead of memorizing different formulas for each GST rate, remember that the calculation method remains the same—the only difference is the GST percentage. For quick and error-free calculations, use our GST Calculator, which supports GST addition, GST removal, and GST calculations for all major tax slabs used in India.