The number you need, worked out properly
Calculators for one job each, done properly: GST split into CGST and SGST exactly as an invoice shows it, how long a speech runs, and how much time each mark gets in an exam.
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GST Calculator
Add or remove GST, with the CGST and SGST split.
Add GST to a price or take it out of a total at 5%, 18%, 40% and the special rates, with the tax split into CGST and SGST or shown as IGST. Same engine as the GST Calculator app. No sign-up.
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Speech Time Calculator
How long your speech runs, or how many words to write.
Paste a speech or type a word count to see how long it takes to say, or start from the minutes you have and get a word target. Pace presets, pauses and slides, and words counted the way the teleprompter counts them.
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Exam Time Calculator
Minutes per mark, and a finish-by time for each section.
Type the exam length, marks, reading and checking time to get minutes per mark, time per question and the clock time to finish each section by. CBSE presets checked against the board's papers.
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How the calculators work
Adding GST or taking it out
There are two questions a GST calculator answers. Adding GST starts from a price before tax and works out the tax and the total: ₹1,000 at 18% is ₹180 of GST and ₹1,180 to pay. Taking GST out starts from a total that already includes tax and works backwards to the price before it, which is what you need when a bill or a quote only shows the final amount. ₹1,180 at 18% comes back to ₹1,000 and ₹180, not ₹1,180 minus 18%.
The rate buttons cover 5%, 18% and 40%, the three main slabs since 22 September 2025, plus 3% for gold and jewellery, 0.25% for rough diamonds and 0%. Any other rate up to 40%, such as 12% for an old invoice, goes in the Other box.
CGST and SGST, or IGST
A sale inside one state is taxed as CGST and SGST, half each. A sale from one state to another is taxed as IGST, the whole rate in one line. The calculator shows whichever split you choose, rounded the way an invoice is: the tax is rounded once, and when it cannot be halved evenly the extra paisa goes to CGST, so the two halves always add back to the total tax.
Words to minutes, for a speech
The speech time calculator divides a word count by a speaking pace: 650 words at 130 words a minute is 5 minutes. Paste the speech and it counts the words the same way the teleprompter does, or start from the time you have and it gives the most words that fit, rounded down so the speech does not run over. Pace presets run from a slow 110 to a fast 170 words a minute, with room for pauses and slides.
Minutes per mark, for an exam
The exam time calculator takes the time kept for checking off the end of the paper and shares the rest out by marks. A CBSE 3-hour, 80-mark paper with 15 minutes for checking gives 2.06 minutes a mark. Add the sections and it gives each one a finish-by time on the clock, which you can print and keep beside you in a mock paper.
What they will not do
The GST calculator calculates and explains. It does not file returns, connect to the GST portal or keep accounts, and it is not a government service. For anything you file, check the rate against the CBIC notification for your goods or service. The guides below cover the cases people most often get wrong: restaurant bills, gold jewellery, HSN codes and which of CGST, SGST and IGST applies.
The speech and exam calculators plan the time but do not run a clock; the speech timer and the exam clock do that. Their paces are typical figures for English speech, and their presets follow CBSE's own papers, so check the instructions on your paper.
Before you open one
Which GST rates does the calculator cover?
5%, 18% and 40%, plus the special rates. It adds GST to a price or takes it out of a total, and splits the tax into CGST and SGST or shows it as IGST.
How long does a speech of a given length take?
Paste the speech or type a word count into the speech time calculator and it shows the time at your chosen pace, with pauses and slides added. Start from the minutes instead and it gives a word target.
How much time should I spend on each question in an exam?
Type the exam length, marks and reading and checking time into the exam time calculator. It gives minutes per mark, time per question and the clock time to finish each section by.
Are the calculators free?
Yes, with no sign-up. The GST calculator uses the same engine as the GST Calculator app on Google Play.
Guides for these tools
CGST, SGST or IGST: which one goes on your invoice, and how to split it
Within a state, GST splits into equal CGST and SGST. Across state lines it is one IGST line at the full rate. How to tell which applies, with worked splits.
6 min readGST on gold jewellery: 3%, making charges, and how to check the bill
Gold jewellery carries 3% GST, a rate GST 2.0 left alone. How making charges are taxed, where the 5% rate applies, and how to check a jeweller's bill.
6 min readGST on a restaurant bill: how to check it's charged right
Most restaurants charge 5% GST, as 2.5% CGST and 2.5% SGST. When 18% is right, why service charge is optional, and how to check a bill in thirty seconds.
6 min readHow long is a 1,000-word speech? Times from 500 to 2,000 words
A 1,000-word speech takes about 6 minutes 40 seconds to 7 minutes 42 seconds at a normal pace. Times for 500 to 2,000 words, with pauses and slides.
5 min readHow many words for a 60-second video script, and how to write one that reads well
At 140 to 160 words a minute, a 60-second video is about 140 to 160 words. Word counts for 15 to 180 seconds, and how to write a script that sounds spoken.
6 min readHow many words is a 5-minute speech? Word counts from 1 to 20 minutes
A 5-minute speech is about 650 to 750 words at a normal pace. Word counts from 1 to 20 minutes, how to find your own pace, and how to time a practice run.
6 min read
Looking for something else?
Device tests, the speech timer and exam clock, a photo metadata remover and a voice recorder — all free, all in the browser.