# GST, VAT and sales tax calculator

> Add GST, VAT or sales tax to a price, or remove it from a tax-inclusive price, with stacked state and local rates or India's CGST/SGST split.

Interactive version: https://www.calcopenly.com/finance/gst-vat-sales-tax-calculator
Subject: Finance calculators

Adding tax multiplies the pre-tax price by (1 + rate ÷ 100). Removing tax from a tax-inclusive price divides by the same factor; multiplying the inclusive price by the rate would overstate the tax. When several rates apply, such as a state and a local sales tax, each is charged on the pre-tax price and the amounts are added.

With the defaults, 1,000 at a 6.25% state rate plus a 2% local rate, the Texas maximum combination, carries 82.50 of tax, 1,082.50 in total. Under India's GST, an 18% rate on 1,000 adds 180: 90 of CGST and 90 of SGST for a sale within a state, or 180 of IGST for a sale between states.

The rates are the ones you enter, so check the current rate for the product and the place of sale. US sales tax is set by state and local governments, so two addresses in the same state can pay different rates.

## Inputs

- **I want to** (options: Add tax, Remove tax)
- **Amount**: The price before tax when adding tax; the price including tax when removing it
- **Tax type** (options: Sales tax or VAT, India GST)
- **Tax rates (%)**: Separate several rates with commas (for example state 6.25 and local 2); each applies to the pre-tax price. UK VAT is 20, EU standard rates run 17–27.
- **GST rate**: Slabs from 22 September 2025: 5% and 18%, 40% for specified goods, 3% for gold
- **Supply** (options: Within a state (CGST + SGST), Between states (IGST))

## Results

- Tax amount — main result
- Price before tax
- Price including tax
- Combined rate
- CGST
- SGST / UTGST
- IGST

## Formula

$$
\text{Add: } G = N\Big(1 + \tfrac{\sum r_i}{100}\Big) \qquad \text{Remove: } N = \frac{G}{1 + \sum r_i / 100}
$$

## Worked examples

### Add 18% GST within a state

- I want to: Add tax
- Amount: 1000
- Tax type: India GST
- GST rate: 18%
- Supply: Within a state (CGST + SGST)
- **Tax amount: 180.00**
- **CGST: 90.00**
- **SGST / UTGST: 90.00**
- **Price including tax: 1,180.00**
- Checked against: Python decimal: 1000 × 0.18 = 180, split equally between CGST and SGST

### Remove 20% VAT from 120

- I want to: Remove tax
- Amount: 120
- Tax type: Sales tax or VAT
- Tax rates (%): 20
- **Price before tax: 100.00**
- **Tax amount: 20.00**
- Checked against: HMRC VAT fraction for the 20% rate is 1/6: 120 × 1/6 = 20; Python decimal 120 / 1.2 = 100

### State 6.25% plus local 2% on 100

- I want to: Add tax
- Amount: 100
- Tax type: Sales tax or VAT
- Tax rates (%): 6.25, 2
- **Tax amount: 8.25**
- **Price including tax: 108.25**
- **Combined rate: 8.25%**
- Checked against: Python decimal: 100 × 0.0625 + 100 × 0.02 = 8.25

### Zero rate

- I want to: Add tax
- Amount: 500
- Tax type: Sales tax or VAT
- Tax rates (%): 0
- **Tax amount: 0.00**
- **Price including tax: 500.00**
- Checked against: 500 × 0 = 0 by definition

### Remove 18% IGST from 2360

- I want to: Remove tax
- Amount: 2360
- Tax type: India GST
- GST rate: 18%
- Supply: Between states (IGST)
- **Price before tax: 2,000.00**
- **IGST: 360.00**
- Checked against: Python decimal: 2360 / 1.18 = 2000; 2360 − 2000 = 360

### Remove stacked 8.25% from 54.13

- I want to: Remove tax
- Amount: 54.13
- Tax type: Sales tax or VAT
- Tax rates (%): 6.25, 2
- **Price before tax: 50.00**
- **Tax amount: 4.13**
- Checked against: Python decimal: 54.13 / 1.0825 = 50.0046…; tax 4.1254…

## Questions

### How do you calculate sales tax?

Multiply the pre-tax price by the combined rate. At 8.25%, a 100 purchase carries 8.25 of tax. In Texas that combined rate is the 6.25% state rate plus the maximum 2% of local taxes; California's statewide rate is 7.25% before local additions. Oregon, Montana, New Hampshire, Delaware and Alaska have no general state sales tax, although Alaskan localities may levy one.

### How do you remove VAT from a price?

Divide the VAT-inclusive price by 1 plus the rate. At the UK standard rate of 20%, 120 ÷ 1.2 = 100, so the VAT is 20, which is also 1/6 of the inclusive price: HMRC's VAT fraction for the 20% rate (VAT Notice 700). The UK's other rates are 5% (reduced) and 0% (zero-rated), and since 1 April 2024 businesses must register once taxable turnover passes £90,000.

### How is GST split into CGST, SGST and IGST?

Within a state, the GST rate is split equally between central GST (CGST) and state GST (SGST, or UTGST in a union territory); between states, the full rate is charged as integrated GST (IGST). At 18% on 1,000, that is 90 of CGST plus 90 of SGST, or 180 of IGST. Since 22 September 2025 the main GST rates are 5% and 18%, with 40% for specified goods.

### What are the VAT rates in the EU?

Each member state sets its own standard rate, which the VAT Directive (article 97) requires to be at least 15%. At 1 July 2025 the lowest standard rate was Luxembourg's 17% and the highest Hungary's 27%; Finland charges 25.5%, Estonia 24% from 1 July 2025 and Romania 21% from 1 August 2025 (European Parliament research briefing, January 2026).

### How accurate is the GST, VAT and sales tax calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 6 worked examples whose answers come from independent sources; for example, “Add 18% GST within a state” is checked against Python decimal: 1000 × 0.18 = 180, split equally between CGST and SGST.

### Where does the method come from?

GOV.UK — VAT rates; PIB — Recommendations of the 56th GST Council meeting (rates from 22 September 2025); CBIC — GST concept and status (CGST, SGST/UTGST, IGST).

## Sources

- [GOV.UK — VAT rates](https://www.gov.uk/vat-rates)
- [PIB — Recommendations of the 56th GST Council meeting (rates from 22 September 2025)](https://www.pib.gov.in/PressReleasePage.aspx?PRID=2163555)
- [CBIC — GST concept and status (CGST, SGST/UTGST, IGST)](https://cbic-gst.gov.in/)

_Note: financial information, not professional advice._