Made for shop owners, accountants and small businesses

GST Calculator – Add or Remove GST Amount Online

This free GST calculator by Volvo Computer Technology helps you quickly calculate GST on any amount. You can add GST to a basic value or remove GST from an inclusive amount and see the split between CGST, SGST and the total invoice value.

Quick GST Calculator

Select whether your amount is before GST or including GST, set the rate and see the full breakdown instantly.

Note: This calculator is for quick estimation based on standard GST rates (5%, 12%, 18%, 28%). For compliance, always cross-check with your accountant or billing software reports.

How GST calculation works (simple explanation)

1. Adding GST to a base amount

Suppose your basic amount is ₹1,000 and GST rate is 18%. Then:

GST = 1,000 × 18% = ₹180
CGST = 9% of 1,000 = ₹90
SGST = 9% of 1,000 = ₹90
Invoice total = ₹1,000 + ₹180 = ₹1,180

2. Removing GST from an inclusive amount

If the price ₹1,180 already includes 18% GST, the base amount is calculated as:

Base amount = 1,180 × 100 ÷ 118 ≈ ₹1,000
GST amount = 1,180 − 1,000 = ₹180
CGST = ₹90 and SGST = ₹90

Our calculator does the same logic for any amount and any GST rate you enter.

Useful for shops, services and online sellers

A GST calculator is handy for many daily use cases – from retail counters to online sellers and service providers.

Checking invoice values before printing bills.
Explaining GST split (CGST + SGST) to customers.
Converting tax-inclusive prices into net values for accounting.
Preparing quotations and proforma invoices with GST.
Verifying totals from Excel or billing software outputs.

If you are using Marg ERP or similar billing software, this online GST calculator can be used as a cross-check tool when designing invoice formats and price lists.

GST tax slabs commonly used in India

The most frequently used GST slabs for goods and services are 5%, 12%, 18% and 28%. Different categories of items fall under different slabs as per government notifications. The calculator on this page is flexible – you can type any rate, not only fixed slabs.

GST rate	Typical usage (examples only)
5%	Essential items, some food products and basic goods.
12%	Certain processed foods, packaged products and daily use items.
18%	Most services, electronics, computer peripherals and IT services.
28%	Selected luxury goods and specific high-end products.

How to use this GST calculator effectively

Decide whether your amount is before GST or including GST.
Enter the amount and choose the GST rate (e.g. 18% for many IT services and electronics).
Select the calculation mode – add or remove GST.
Use the breakdown to understand base value, total GST, CGST and SGST.
Use these values in your invoices, quotations or internal costing sheets.

Frequently asked questions (FAQ)

Is this GST calculator valid for all Indian states?

Yes, the calculation logic for CGST and SGST is the same for all states where intra-state supply applies. For inter-state transactions, IGST is applicable, but the total GST percentage remains the same. You can still use this calculator to get the total GST amount.

What is the difference between CGST, SGST and IGST?

For sales within the same state, GST is split into CGST (Central GST) and SGST (State GST), usually 50-50 of the total rate (for example 9% + 9% for 18% GST). For inter-state sales, a single IGST (Integrated GST) applies at the full rate. This calculator shows CGST and SGST split, but the total GST amount remains equal to what you would pay as IGST.

Can I rely on this tool for filing GST returns?

This calculator is a supporting tool for quick estimations and understanding invoice values. For filing GST returns and final compliance, always depend on your accounting software, ERP system or professional advice from your CA.

Why is the base amount different when I remove GST?

When you remove GST from an inclusive amount, the base is calculated by dividing the total by (100 + rate) and multiplying by 100. Due to rounding rules, there can be a difference of a few paise. Our calculator shows values rounded to two decimals for clarity.

Can I integrate this GST calculator into my own website?

If you are a web developer or business owner, you can take inspiration from the structure of this page and create a similar calculator in your own branding. For full billing and inventory control, consider using a dedicated billing software like Marg ERP, which also handles GST, stock and reports in one place.