Add GST to a base amount, or remove GST from a GST-inclusive price.
To add GST to a base amount: GST amount = base × (rate / 100), final price = base + GST. To remove GST from a GST-inclusive price: base = inclusive ÷ (1 + rate/100), GST amount = inclusive − base.
Small business owners and freelancers reach for a GST calculator most often when quoting a client, since a price can be discussed either inclusive or exclusive of tax and mixing the two up leads to under-charging or an awkward correction later. Shop owners and e-commerce sellers use it to work backward from a GST-inclusive MRP to find the base price and tax component separately, which is needed when filing returns or reconciling books against the GST charged on each invoice. It's also useful at the consumer end — checking a restaurant bill or invoice to confirm the GST charged matches the stated rate, since billing errors do happen. Because India's GST system uses multiple slabs (5%, 12%, 18%, 28%) depending on the category of goods or services, professionals dealing with mixed product lines often switch between rates repeatedly through a workday rather than using one fixed percentage. Comparing two vendor quotes that present pricing differently — one inclusive, one exclusive of tax — is another common reason to run both through the same calculator before deciding which is actually cheaper.
GST amount = base amount × (rate / 100). The final price is the base amount plus the GST amount.
Base amount = inclusive price ÷ (1 + rate/100). Subtract the base amount from the inclusive price to get the GST amount.
In India, the common GST slabs are 5%, 12%, 18%, and 28%, depending on the category of goods or services. You can also enter any custom rate.