GST & Sales Tax Calculator
Add tax to a price or strip it back out of a tax-inclusive total.
Net amount
1,000.00
Tax (18%)
180.00
Gross total
1,180.00
Use this tool to add sales tax or GST to a price, or to reverse the calculation and pull the tax back out of a tax-inclusive total — both are common but easy to get wrong by hand, especially the reverse case.
Set any tax rate you need — GST, VAT, or a general sales tax — and switch between adding tax to a net price and extracting it from a gross price.
Adding tax versus extracting it
Adding tax is straightforward: multiply the net price by (1 + rate). Extracting it is where people go wrong, because the instinct is to take the rate off the gross figure — and that gives the wrong answer every time.
| Direction | Formula | Example at 18% |
|---|---|---|
| Add tax to net price | net × (1 + rate) | 1,000 → 1,180 |
| Extract tax from gross | gross ÷ (1 + rate) | 1,180 → 1,000 |
| Wrong way to extract | gross × (1 − rate) | 1,180 → 967.60 ✗ |
The wrong method under-reports the net price by 32.40 on a 1,180 invoice, because 18% of the gross is a larger sum than 18% of the net.
Common rates around the world
| Country / region | Standard rate | Name |
|---|---|---|
| India | 5% / 12% / 18% / 28% | GST (slab-based) |
| United Kingdom | 20% | VAT |
| Australia | 10% | GST |
| Canada (federal) | 5% | GST, plus provincial tax |
| Singapore | 9% | GST |
| European Union | 17%–27% | VAT, varies by member state |
Rates change and many goods sit in reduced or zero-rated categories. Confirm the rate that applies to your specific product before invoicing.
Frequently asked questions
- How do I remove tax from a total that already includes it?
- Divide the tax-inclusive total by (1 + tax rate). For example, at 10% tax, divide by 1.10 to get the pre-tax amount.
- Is this the same as a VAT calculator?
- Yes — GST, VAT, and general sales tax all work the same way mathematically; only the rate and name differ by country.
- Can I use this for compound or multiple tax rates?
- This tool applies a single flat rate. For layered taxes, apply each rate to the running total in sequence.
- What is the difference between CGST, SGST and IGST in India?
- They are splits of the same total rate. An 18% intra-state supply is 9% CGST plus 9% SGST; an inter-state supply is 18% IGST. The amount the customer pays is identical either way.
- Why does my invoice total differ by a cent from the calculator?
- Rounding rules differ — some systems round the tax on each line item, others round only the invoice total. Over many lines the two approaches can drift by a cent or two.
Read more on this
- Percentages, discounts and tax: the errors that cost moneyWhy stacked discounts never add up, how to pull tax out of an inclusive total correctly, and why a 20% rise isn't undone by a 20% fall.
- How GST works: slabs, forward vs reverse calculation, and input creditA clear guide to GST slabs, CGST/SGST vs IGST, extracting base price from gross invoices, and how input tax credit prevents cascading taxation.