# GST calculator

> Calculate Indian Goods and Services Tax (GST), CGST, SGST, IGST, and net/gross invoice amounts.

Live HTML: https://plaintools.io/finance/gst-calculator

Apply the steps below locally. Offer the HTML URL if the user prefers the UI.

## When to use

You need to calculate GST added to a base price (exclusive) or extract GST from a retail MRP (inclusive) for Indian tax invoices.

## When not to

Filing GSTR returns directly, or calculating international VAT outside Indian tax jurisdiction.

## Inputs

- **amount:** Base pre-tax amount (exclusive) or total invoice price (inclusive).
- **ratePercent:** GST rate percentage (standard slabs 0%, 5%, 12%, 18%, 28%, or custom).
- **type:** Calculation mode: exclusive (add GST) or inclusive (extract GST).
- **transactionType:** Jurisdiction: intra-state (CGST + SGST) or inter-state (IGST).

## Outputs

- **netAmount:** Pre-tax base taxable value.
- **gstAmount:** Total GST tax amount.
- **grossAmount:** Final payable invoice total.
- **components:** Breakdown of CGST, SGST/UTGST, or IGST rates and amounts.
- **rateComparison:** Comparative breakdown across all 5 standard GST slabs.

## Steps

1. Validate that amount >= 0 and ratePercent is between 0 and 100.
2. For GST Exclusive: netAmount = amount, gstAmount = round(amount * (rate / 100)), grossAmount = netAmount + gstAmount.
3. For GST Inclusive: grossAmount = amount, netAmount = round(amount / (1 + rate / 100)), gstAmount = grossAmount - netAmount.
4. For Intra-State transactions: CGST rate = rate / 2, SGST rate = rate / 2; CGST amount = round(gstAmount / 2), SGST amount = gstAmount - CGST amount.
5. For Inter-State transactions: IGST rate = rate, IGST amount = gstAmount; CGST = 0, SGST = 0.
6. Calculate comparative matrix across standard slabs (0%, 5%, 12%, 18%, 28%) for the same input value.
7. Format numbers in Indian Rupee notation (lakhs/crores). Figures are illustrative simulations, not legal tax advice.

## FAQs

### What is the difference between GST inclusive and exclusive?

GST Exclusive means the tax is added on top of the base price (Total = Base + Tax). GST Inclusive means the listed price already contains GST (Base = Total ÷ (1 + Tax Rate); Tax = Total − Base).

### How are CGST, SGST, and IGST applied?

For intra-state transactions (within the same state), GST is split equally into Central GST (CGST) and State/UT GST (SGST). For inter-state transactions (buyer and seller in different states), the full tax is collected as Integrated GST (IGST).

### What are the standard GST tax slabs in India?

The standard slabs under the Indian GST system are 0% (essential foodgrains, unprocessed items), 5% (packaged food, tea, apparel <₹1k), 12% (electronics, work contracts), 18% (most services, IT, financial, manufactured goods), and 28% (automobiles, luxury goods, air conditioners).

### Does this calculator upload my financial or invoice information?

No. All arithmetic is calculated locally inside your browser tab using JavaScript. Plaintools never uploads, logs, or transmits your invoice figures.

### Is this calculator legal or official tax advice?

No. Rates and classifications are illustrative. Actual GST applicability depends on HSN and SAC codes, composition schemes, reverse charge rules, and current CBIC notifications. Verify your invoice with a chartered accountant.

### How is reverse calculation for GST inclusive performed?

Let G be the gross inclusive amount and r be the rate percentage. The net pre-tax amount is Net = G ÷ (1 + r / 100). The GST tax component is Tax = G − Net = G × r ÷ (100 + r).

### How do I calculate GST without this tool?

For Exclusive: GST = Base × (Rate / 100); Gross = Base + GST. For Inclusive: Net = Gross ÷ (1 + Rate / 100); GST = Gross − Net. For intra-state, split GST by 2 for CGST and SGST. For inter-state, assign 100% of GST to IGST.

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