The free online GST and GST Free Portion Calculator! Provided here for your use. Please make sure you report any issues with the calculator in the comments below. Enjoy your calculations!

I wrote this simple little script in JavaScript to help me calculate Australian GST (10%) today. Being such a useful little script, I thought I would post it.

Please feel free to use this script as your require, if you wish to have this script on your own website please post an acknowledgement and link back to this page.

**How to Calculate GST the hard way (using you know, numbers and shit)**

If you have something without GST, and you need it with GST, you add 10%. Which is easilest done on a calculator by multiplying your amount by 1.1 (which is really saying mister Calculator, give me 110% of this amount).

`$100 * 1.1 = $110`

To go the other way, let's say we have $110, which includes 10% GST already. Working out how much is the GST part is quickly done on a calculator by dividing by 11. Not 10 you say? No, 11. Because easiestly explained, before GST you had 10 parts of a number, the "extra" 10% is another "part". So we need to work out what that part is.

`$110 / 11 = $10`

Huzzah! We have the GST component of an amount! Now, we need to take that GST part from our original amount of $110 to get what the amount is without GST.

`$110 - $10 = $100`

Perfect :-)

But seriously, why do all this manual work when this GST calculator does it for you?

Last Updated 04/03/2014: Fixed floating point arithmetic (Loss of 1c on some calculations). Thanks to Michael for pointing it out.

Hi Darren,

I’m trying to calculate interest on overdue fees and was wondering if you could please help me.

Say someone owes $396.00 from the 1/01/2013, so they are 466 days overdue (i’m typing this on 12/04/2014) and the annual interest rate is 10%, how would work out the DAILY interest rate??? my computer works out the total figure, but i need to know the cost per day???

Than k you

I’ve never been very good with interest calculations. http://www.wikihow.com/Calculate-Daily-Interest is probably the easiest I can find. It’s dependant on when interest is charged (is it charged per day, per month, per year?) Different financial institutions do it differently, if you’re making up the details – just be clear with it when asking someone to paid said interest.

Cheers, sorry I can’t be more help.

Hi Darren , hoping you can enlighten me – I have multiple insurance policies paid monthly in one combined deduction from my bank account. The first monthly premium is always a little more than the remaining 11, therefore unable to divide annual breakdown by 12 (annual breakdown available ). I am apparently unable to obtain the monthly breakdown ie base premium, GST & stamp duty components from my insurance company, but still have to input into my accounting programme on a monthly individual item basis. If to find GST in a number you divide by 11 what does one divide by to find say 9%? I presume this is the reverse equation: total amount deducted from bank account less government stamp duty at say 9% (for car) less GST equals base premium. Note stamp duty is calculated on the premium inclusive of GST. Hope you can help stop me going grey

Finding % of something. Well, if you have some numbers I can play and show working (you know, double check myself), but the following should work in all cases.

Say you have $550 premium. This includes GST, which is added on a 9% stamp duty of the total amount. So we first need to remove GST. Using the above calculator, I can tell you know that’ll be the following (in lots of numbers);

Assuming stamp duty is _before_ GST. If it’s not before, do these sums the other way around.

550 / (1 + 0.10) = $500 (Where the .10 is 10% added to a ‘whole’ of 1) or 1.1

500 / (1 + 0.09) = $458.72 is the premium before stamp duty. (Where the 0.09 is 9% added to a ‘whole’ of 1) or 1.09.

So let’s do this another way, because we can.

GST

x + (10% of x) = 550

x + (10/100 * x) = 550

1x + 0.1x = 550

1.1x = 550

x = 550 / 1.1 = $500 (Hey look, $550 – $500 is the 10% we wanted, $50 GST.)

Stamp Duty

x + (9% of x) = 500

x + (9/100 * x) = 500

1x + 0.09x = 500

1.09x = 500

x = 500 / 1.09 = $458.72 (AWESOME. Above math logics worked. So stamp duty is $500 – $458.72 = $41.28).

Double check ourselves again putting the parts together calculated. $458.72 + $41.28 (stamp duty) = $500 * 1.1 (gst) = $550 total.

Make sense? I think it does… but as usual, get a professional to check my work xD

Also – I’m not actually sure if GST would be applied on top of stamp duty. So you’d need to triple check with someone if that’s the case. I think GST and Stamp Duty would be applied independently of each other – because they’re both different taxes.

But as always – double check me

(Also if this is the case, the math would change yet again…)

Good app but why does it not calculate gst-able from 9 cents GST out of a total of 40.55?

Also with similiar amounts.

Can you please let me know what calculator you’re trying to use and the values for everything you’re entering, and what you would expect?

Cheers,

GST-Free Portion Calculator?

Total: 40.55

GST Stated: 0.09 ?

I was just testing your calculator. If I put in 9.95 and click ‘Add Tax’ the total does not equal cost + GST. Shouldn’t the answer be $1.00 GST & $10.95 total as per the rounding and calculations from the ATO?

http://www.ato.gov.au/Media-centre/Media-releases/Certainty-for-business-in-GST-calculations-and-rounding/

You’re right.

I’ll fix this up tonight.

Fixed that up! Thank you for bringing it up

Thanks Dazz for posting and sharing the script … and no, you are not to talking to yourself, just the computer

you have just saved my butt!! thanks so much, bookmarked and saved

Thanks you explained in detail and I will use your calculator to assit me at work.

Hi Darren,

You are literally a life saver, I work in an Accounts position and am constantly trying to figure out on invoices whether the amounts are correct (i don’t trust my own calculations). Until now, i have had some serious issues with other calculators. I did have a really good on bookmarked but they deleted it (go figure!)

Thanks again

- Taelar.

You’re welcome ^_^

Hi Darren quick question although it may seem long. My wife and i are starting our own business from home. i wont go in to to much detail about what we do however we will be agents for our clients etc. Now say our client had a massive sum of mmm lets say $44,432.25 that we had earned for them. If our agent fee was 15% of that total + gst how would we go about making that calculation to make sure we take the correct gst? if that makes sense.

Would we divide the total ($44,432.25) by 1.15 to get our 15% fee which in this case = $5,795.52 and then do we add the gst onto our fee total? So $5795.52 * 1.1 = $6,375.07 which is then $579.55 gst? I think thats right. Meaning they would be left with a balance of $ 38,057.18 owing to them. This then meaning our agent fee would be $6,375.07 Gst incl? am i right here or way off hahaha? hope i’m close

$44,432.25 Earned. You charge 15% of this amount as your service fee. Wouldn’t that be $6,664.84 before tax?

Calculated:

$44,432.25 * 15% = $6,664.8375

$44,432.25 * 0.15 = $6,664.8375

To check that’s right, 15 can fit into 100, 6.666666 times (100 / 15).

My calculation 6,664.8375 * 6.666666 = 44,432.24556. (Off slightly due to rounding and the 6.66 reoccurring.)

That amount, $6,664.8375

$7331.32 including GST

$6664.84 without GST

$666.48 GST.

If you’re taking that amount away from the total amount as to whom gets what, that’d be $37100.93 owing to them.

As always, double check with an accountant.

Thanks very much for that, I was unsure like I said but that seems to make sense. Cheers again.

I the amount of $44,432.25 inc GST?

If so, your commission is 15% of that amount total.

Generally commission is paid on the amount EX. GST.

Usually true. Take note Shanzo.

Awsome app saves me sow much time thanks.

That’s all good and Fair and i can see the simplicity in it

Or.. You could just right a script in MySQL Which does Exactly the same thing

SELECT {ex GST Amount},{GST Amount},{Inc GST Amount} FROM {TABLE NAME};

And you get the same thing, and it relates to your data

On another point, Without Bagging this app.

When you get too comfortable with Automation

YOU GET LAZY

And then… of course, You have this

What if a person like me, for example, Prefers to do it the long way.

and then you have this..

Your not going to use this app unless your involved with business in some way

so.. Your a business owner or Book keeper or Accountant

now.. that in mind, you should not get complacent about knowing how to do it manually, especially since it would be your trade

Which is why i appreciate the Author of the app, actually specifying how to do it

in my opinion people who get reliant on Automated stuff

are usually the people who ask me questions that they should already know

example

I’m a computer engineer

and then i get other engineers from time to time asking me stuff like

Martin, Do you know how to convert a Decimal number like 134 for example, to Binary

I’ve used a Decimal to Binary converter and i know the answer is 10000110

But how do i do it manually

See My Point

and .. These guys claim to be engineers

Automation is Good and is efficient, BUT DON’T GET LAZY IN THE PROCESS.

Just my Opinion

Seriously Martin do you have nothing better to do with your time than to babble nonsense!!!

Bookmarked! Finally, a simple solution to calculate GST. Thank you Darren!

Thanks for your clear and simple explanation of the calculation, love the calculator too, I’ve added it to my bookmarks.

Cheers,

^_^

Thanks- i’m a bit lazy ; )

Completely acceptable

Um, either my Telstra bills suck even more or the calculator isn’t quite right. Quite often I put in some figures and it says it is unable to calculate. It is normally with my Telstra bills – but that is the main thing I use the calculator for because every other company in the world is normal and give you a lovely break up! I do love your product though….I am sure it is Telstra and not you…eg total $364.20 Gst $33.11

Unable to Calculate comes from the GST Free Portion calculator yes?

Of the amount $364.20, if the amount was entirely GST inclusive – you’re looking at $33.10909 gst. So they’ll round up to $33.11. There is no GST Free portion of this amount. So unable to calculate is simply saying – there isn’t GST Free in this portion.

Otherwise, please give me all your figures you’re entering in, and I’ll take a look later tonight.

Cheers,

Hey thanks you’ve really saved me in my Tafe course !!

Hello Daren, this is a very simple question for you I guess. But I am trying to use the GST formula on Excel but seemed that I am missing something. Could you please show me how. =sum(C1????) many thanks

Amy

Depends what you’re trying to work out.

If you have an amount in A1 for example, that needs to have GST added, use =A1*1.1

If you have an amount in A1 that includes GST, that needs to have GST removed, use =A1-(A1/11)

I have your GST calculator saved in my Favourites and use it all the time.

Very glad to hear it

Hey, I think your GST Calculator is awsum.

Thanks Kaz

No worries at all ^_^

Android and iOS apps coming to a store near you… stay tuned

good work mate

Thanks great website and love the paypal fee calculator too.

Now if only you could figure out Ebay fees for me!

ooo. Perhaps I could.

http://pages.ebay.com.au/help/sell/fees.html#Store

Talk about complicated. Depends on the item sold and if you’re a business or just a typical Joe. And then if you have enough free-listed-items in the month.

This requires some thought. And thinking hurts.

Thanks. Saved from pulling my hair