Numarly

GST Calculator (India)

Calculate GST amount, total price, and reverse GST instantly

What is it?

This GST calculator helps you calculate Goods and Services Tax (GST) in India. You can add GST to a base amount to find the total price, or remove GST from a total amount to find the original base price.

Formula

Add GST: Total = Amount + (Amount × GST%)

Remove GST: Base = Total ÷ (1 + GST%)

Formula Explanation

Adding GST simply applies the tax percentage on top of the base amount. Removing GST works differently — you can't just subtract the percentage from the total, since the GST% was originally calculated on the smaller base amount, not the total, so dividing by (1 + GST%) is required to correctly back out the original base.

Example Calculation

Adding 18% GST to ₹1,000: GST = ₹180, total = ₹1,180. Removing 18% GST from a total of ₹1,180 correctly returns a base of ₹1,000.

How to Use

  1. Enter the amount.
  2. Select the applicable GST rate (5%, 12%, 18%, or 28%).
  3. Choose whether to Add GST or Remove GST.
  4. Click Calculate GST to see the base amount, GST amount, and total.

Benefits

  • Handles both adding and removing GST in one tool.
  • Covers all four standard Indian GST slabs.
  • Avoids the common mistake of directly subtracting a percentage to reverse GST.

Use Cases

  • Checking whether a retailer or invoice has applied GST correctly.
  • Calculating the pre-tax cost of an item from its GST-inclusive price.
  • Small business invoicing and pricing calculations.

What Your Result Means

The base amount is the price before tax, the GST amount is the tax itself, and the total is the final price a customer pays (base + GST). All three numbers should always satisfy Base + GST = Total.

Tips

  • Always confirm which GST slab applies to your specific goods or service category.
  • Use "Remove GST" when you have a GST-inclusive price and need the pre-tax base.
  • Double-check by adding the base and GST amounts back together — they should equal the total.

Common Mistakes

  • Subtracting the GST percentage directly from a total price instead of dividing by (1 + GST%).
  • Using the wrong GST slab for a given category of goods or services.
  • Confusing GST-inclusive and GST-exclusive prices when comparing quotes.

FAQs

What is GST?

GST (Goods and Services Tax) is an indirect tax applied to the supply of goods and services in India, replacing many previous indirect taxes.

How do I calculate GST on a price?

Multiply the base amount by the GST rate percentage, then add that to the base amount to get the total price including GST.

How do I remove GST from a total price?

Divide the total amount by (1 + GST rate as a decimal) to find the original base price before GST was added.

What are the common GST slabs in India?

The most common GST rates in India are 5%, 12%, 18%, and 28%, applied to different categories of goods and services.

Why can't I just subtract the GST percentage from the total to remove it?

Because the GST percentage was calculated on the smaller base amount, not the larger total — subtracting the percentage from the total overestimates how much GST was actually included.

GST rates and rules may change over time; confirm the current applicable rate for your specific goods or service.

Last updated: July 25, 2026