Susan enjoys answering questions and helping her readers solve problems while learning more about education, business, and other fun topics.

Are You Stuck on a Percentage Problem?

Seventy percent off is almost always a bargain if you're shopping. But it's good to know how to calculate percentages in your head (or even on paper) so you'll know for sure if you're getting a good deal. And if you're taking an important math test, well, you really need to know how to work with percentages.

In this article, you'll learn how to calculate percentages, including 70% off, and you'll discover a few more math tricks you can do in your head. So, the next time you come across a sale or a percentage problem, you'll be able to amaze your friends (and yourself) by figuring out the solution—calculating percentages in your head faster than a speeding shopping cart.

No matter what your age is, if you have a working knowledge of basic math, you can learn math tricks and shortcuts to make calculating percentages and doing other mental math easy.

What is a percent, anyway?

"Percent" simply means "parts out of one hundred."

(per = parts out of; cent = one hundred)

For example, one penny = one cent coin, so one penny out of a dollar is 1%.

First, Review the Basics of Percentages

In our explanation, we'll be using some of the information found in the video below. It's just over 10 minutes long, but that will be time well spent reviewing or learning the basics of percentages, as well as practicing to become familiar and comfortable with using this method of mental math.

Step-by-Step Instructions for Calculating 70 Percent Off

Did you watch the video above? If you did, you've probably already solved your 70%-off problem. If not, here's the step-by-step explanation. There are actually two ways to do it.

First, make sure you're asking yourself the right question. If you need to know "What's 70% off?", then what you're actually asking yourself is, "What's 30% on?" Let me explain:

Let's say we're working with $250. We want to know what's 70% off of $250. Well, do we really want to know how much we're going to take off or how much is left after we remove that 70%? Either way of looking at the problem is okay, though one option is a little simpler than the other.

Method 1: Figuring Out 70% of $250 (How Much You're Saving)

1. To calculate 70% of $250, first figure 50% + 10% + 10% (which adds up to 70%), because those numbers are really easy to work with. So, 50% (or half) of 250 is 125; then we move the decimal to the left one place to determine 10% of 250, which gives us 25.0.
2. We get 125 + 25 + 25, which equals 175. Now we know that 70% of $250 is $175. That's how much you're saving!
3. However, we want to know what is 70% OFF of $250, so to get that answer, we take one more step. Subtract $250 - $175, which equals $75. That's how much you're spending.

This isn't difficult math, but there's an easier way. Since we know that when we subtract 70% from 100%, we have 30% left, the amount we're actually looking for is 30% of $250. In other words, we're saving 70% but spending 30%, and we really want to know how much we're going to spend. So why not calculate that in the first place?

Method 2: Figuring Out 30% of $250 (How Much You're Spending)

1. To calculate 30% of $250, think about how 10% + 10% + 10% adds up to 30%. We move the decimal back to the left to get our 10%, so 25.0 is 10%.
2. Next, we either add 25 + 25 + 25 OR we multiply 25 x 3. In either case, we get our answer: $75. That's much quicker and easier than working with the 70% and having to take an extra step to subtract.

So, the bottom line is that "70% off of $250" is the same as "30% of $250." 3 x $25 = $75. That's the sale price—and wow, what a bargain!

A Visual Example of the 30 Percent Method

(In this case, it's easier to do the math with the 3 than the 7.)

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How to Calculate Percentages With a Calculator

There's more than one way to calculate a percentage. If you have a calculator, you'll need to structure the problem a little differently from the way we did it above.

To calculate 70% off on a calculator, think "250 minus 70% equals what?"

Using the calculator, enter the starting number (250 in our example), then the minus sign, then 70 followed by the % key, then the = key to get the answer.

250 - 70% = 75

More Mental Math Videos

To learn more than just percentages, take a look at the other math videos from tecmath on YouTube. You'll need to know how to multiply when you calculate percentages, and this instructor's videos will help teach you shortcuts to make multiplication quicker. There's also a subtraction video. I like this instructor—his voice is kind, and his math methods are magical! You'll love the time-saving tips for working with numbers that you'll learn here.

© 2014 Susan Deppner

Comments: Can you calculate 70% off in your head? Do you have a favorite math shortcut to share? Just want to say hello?

Patricia on June 27, 2019:

I hate math- I have dyslexia and never knew- would memorize the formula and reverse the numbers

Dav on February 13, 2019:

Hi to everyone, I have my own way to do this type of calculations. If I have to know how much is 70% of 250 or another number I do like that:

Everyone knows that 10% is 25 so

25*7 =150.

Sorry for my english and thank you for this article. Gratings from somebody who love to do math calculations in head wythout calculator :)

Susan Deppner (author) from Arkansas USA on July 18, 2016:

Shyron, I'm glad you were able to get back on HP and watch the video. Thanks for taking that extra step and letting me know. Hope you found the video helpful, too! Appreciate your visit and your comment. Have a blessed day!

Shyron E Shenko from Texas on July 18, 2016:

Susan, maybe it is a problem with my computer, I got out of HP and when I came back I could watch the video.

Blessings.

Shyron E Shenko from Texas on July 18, 2016:

Hello Susan, I really like this, math was not my best subject in school. I could not watch the video in this hub it is not there. I think it has something to do with the nit picking niche.

Blessings my friend

Susan Deppner (author) from Arkansas USA on May 26, 2016:

Thank you very much for the feedback, Sunlkunnoth. Appreciate it!

Sunilkunnoth2012 on May 25, 2016:

Hi, I loved this post which contains excellent information. It is helpful too. Thank you for your great job.

Susan Deppner (author) from Arkansas USA on May 25, 2016:

Carol, I am so happy to know that this information was helpful for you and your daughter. Thrilled you could use it! Thanks so much for the comment.

Carol Morris on May 24, 2016:

This was the perfect hub for me to come across today. I've been working with my daughter on her math and I really need to use these resources. Thanks for saving me with this information today!!

Susan Deppner (author) from Arkansas USA on October 27, 2015:

Yes! Coupons are a good example of when we need to know how to calculate percentages in our heads to see if we're really saving money. Thanks for stopping by, Rabadi, and for the follow! (Following you back!)

O from New York on October 26, 2015:

Very useful hubs I often get those coupons in the mail with 20 or 25 percent off on a certain amount it's great to have this trick in your head to help you count, great hub, I am following you :)

Susan Deppner (author) from Arkansas USA on August 18, 2015:

You're welcome, Rachel, and I hope you'll be able to use the tip. Thanks so much for the vote, your kind comment, and definitely the blessings!

Rachel L Alba from Every Day Cooking and Baking on August 18, 2015:

Hi Susan, I really like that idea of figuring out the 30% first instead of the 70%. It works for other percentages too. I was the worse in math in school, many many years ago. lol So thanks for this tip. I voted up and useful.

Blessings to you.

Susan Deppner (author) from Arkansas USA on July 11, 2015:

I know what you mean, Lorelei! We each have our strengths and definitely our weaknesses, especially when math is involved. Thanks for stopping by!

Lorelei Cohen from Canada on July 11, 2015:

Math has always been a terror for me. English for me please. ;)

Susan Deppner (author) from Arkansas USA on June 01, 2015:

Thank you, Akriti!

Susan Deppner (author) from Arkansas USA on June 01, 2015:

Thanks for sharing, Sunil. Appreciated!

Akriti Mattu from Shimla, India on June 01, 2015:

This my friend is such an interesting post for so many shopaholics. voted up :)

Sunil Kumar Kunnoth from Calicut (Kozhikode, South India) on June 01, 2015:

Very interesting and useful hub. Hence shared.

Susan Deppner (author) from Arkansas USA on April 09, 2015:

Ah, good point, Rangoon House. I hadn't thought about that aspect, but certainly it would be very important to be able to do at least a rough calculation when dealing with foreign currencies. Thanks so much!

AJ from Australia on April 08, 2015:

Thank you for this Susan - I need it with the Australian dollar around the percentage of the US dollar at the moment.

Susan Deppner (author) from Arkansas USA on April 08, 2015:

I like that approach to math, shilemarie78. A positive attitude really does make a difference. Thanks so much for the visit and the thumbs up!

Sheilamarie from British Columbia on April 08, 2015:

If you think of math as a puzzle or game, then you can approach it with a positive attitude instead of as something that makes you weak-kneed. You've done a good job of explaining how to calculate percentages-off that I'm sure many will find useful. Voted up as "useful."

Susan Deppner (author) from Arkansas USA on April 05, 2015:

Thanks for that, poetryman! Most children don't think math like this is child's play, but I'm glad you think it is. I appreciate the visit and the kind comment!

poetryman6969 on April 05, 2015:

The 30% remainder trick for the 70% off is very useful. And the fact that you can add up 10% three times makes it child's play!

Vote up for usefulness.

Susan Deppner (author) from Arkansas USA on April 05, 2015:

It can be confusing the first time through, but it makes sense once your mind takes it all in. I can't even imagine dividing by 23, at least not in my head! Happy Easter to you too, Elsie!

Elsie Hagley from New Zealand on April 04, 2015:

Very interesting article, I got lost along the way reading it but I will be back when I'm not so busy, (it easter and visitors coming back for lunch).

The only one I remember when doing GST in New Zealand is 15% - thats multiplied by 3 and then divided by 23, have to do it every three months.

Maybe there's a easier way to do even that.

Hope you are having a happy easter.

Susan Deppner (author) from Arkansas USA on March 11, 2015:

I do that too, PegCole17, and I'm always impressed when cashiers "get it" rather than getting confused! Thanks so much for stopping by.

Peg Cole from Northeast of Dallas, Texas on March 10, 2015:

Doing the math in my head keeps my mind active. I like your explanation of the seventy percent off. I use ten percent a lot since that's so easy to figure and then multiply as needed. I'm one of those people who give the cashier odd change so that I will get back quarters or a five dollar bill rather than four ones and eighty-five cents in coins.

Susan Deppner (author) from Arkansas USA on January 25, 2015:

I agree, Swadhin Kumar, that if we don't use it (math ability) we tend to lose it! Thanks for stopping by!

Swadhin Kumar on January 24, 2015:

It is easier to calculate percentages (usual discounts we get at shops) by breaking them to multiples of 10 and 5. Perhaps we all knew it but forgot it because of long dissociation with elementary mathematics. Thanks.

Susan Deppner (author) from Arkansas USA on January 22, 2015:

Glad I could help, Myra. Thanks so much for the feedback!

Myra on January 21, 2015:

OMG, Thank you Susan for the refresher course on percentages. I was okay with math but not the greatest, I also have forgotten skills of math by not practicing. If you don't use it you lose it. Again, thank you so much, it's so easy the way you explain it.

Susan Deppner (author) from Arkansas USA on November 29, 2014:

Good, really good math teachers seem to be few and far between, Joan. It takes a gifted person to keep the subject "thrilling." I hope you found something here to enjoy. I really liked the math teacher on the videos.

Joan Pope on November 28, 2014:

I was great as a child, but then I had one bad teacher after another, so I gave up on the subject. Later, I had to do maths for Physics, but it wasn't the same, the thrill had gone.

Susan Deppner (author) from Arkansas USA on November 06, 2014:

Thank you for those very kind words, Writer Fox. Parents certainly can be intimidated when it comes to helping their kids with math homework. I hope they find this and find it helpful, too.

Writer Fox from the wadi near the little river on November 05, 2014:

So many kids have trouble doing simple math these days because they are so reliant on online calculators. This is very useful information and I hope many parents and teachers will find your article. Enjoyed, voted up and shared!

Susan Deppner (author) from Arkansas USA on November 03, 2014:

It is nice to have an app for that, Sunshine625! I never thought about the letters versus numbers clash. Perhaps you're onto something there... Thanks so much for stopping by (and for the follow!).

Linda Bilyeu from Orlando, FL on November 03, 2014:

I am so BAD with math. Numbers and I never got along well. Possibly numbers are envious of my love of letters. It's a love hate kind of relationship. Luckily with a calculator on my phone I no longer have to use my brain cells to figure out percentages :)

Susan Deppner (author) from Arkansas USA on September 26, 2014:

I'm a visual learner too, Jemjoseph, so that's how I recognized you. :)

Jemjoseph on September 26, 2014:

Yes, money did come to mind and a teacher once told me that I was a visual learner, how very perceptive SusanDeppner, I'm impressed.

Susan Deppner (author) from Arkansas USA on September 26, 2014:

I definitely agree, Jemjoseph, that the key is in knowing the formula, or at least which formula works for you. Your example makes me think of money. It's easy to divide dollars into quarters, which is where your method starts, I think because it's a very visual process, easy to imagine in your mind. In fact, I think learning styles play a big role in learning math. I'm guessing you're a visual learner. Thanks for your input to the discussion!

Jemjoseph on September 25, 2014:

Great tips for calculating percentages mentally, the beauty about math is that once you know the right formula getting the correct answer is easy. Sometimes there are other formulas that can be applied to find the right answer, in which case it's a matter of choosing the most efficient method.

To find 70% mentally I usually first find 75 % (divide amount by 4 & multiply answer by 3), then subtract 5% (by finding half of 10%), not very efficient I suppose, but it gets the job done.

Susan Deppner (author) from Arkansas USA on July 25, 2014:

@favored: Thanks, I appreciate that feedback!

Fay Favored from USA on July 25, 2014:

Good lesson on the percent process. Math can really be tough sometimes and it's nice to see it explained so clearly.

Susan Deppner (author) from Arkansas USA on July 18, 2014:

@Coffeebreaker: Awesome! It really is fast once you have the concept, which is simple. I think we depend on calculators too much these days, don't you? Thanks so much for commenting!

Coffeebreaker on July 18, 2014:

HI Susan! My mom never bothered helping me with school work,but for 2 times that I still remember this day... how to add 9's and do percent breaking down to 10% times however much and 5% is half of the 10%. I can almost do it faster than someone using a calculator!

Susan Deppner (author) from Arkansas USA on June 27, 2014:

@kimberlyschimmel: Yes, unfortunately. I can see where an excited customer would get confused with two 50 percent off offers combined - unless she did the math! Thanks for the visit!

Kimberly Schimmel from Greensboro, NC on June 27, 2014:

Almost nobody seems to understand percentages any more. I know a retail worker who had an irate customer insisting that an item that was 50% off with an additional 50% off the sale price was free. Logic and math are lost arts for most of the population, unfortunately.

Susan Deppner (author) from Arkansas USA on June 20, 2014:

@ologsinquito2: Oh, my, I absolutely agree with you. I think our brains are just so full of information, there's hardly room for calculations! :)

ologsinquito2 on June 20, 2014:

This is good to know. It takes me longer to calculate anything, now that I've reached middle age.

Susan Deppner (author) from Arkansas USA on June 15, 2014:

@EnthusiasmMadame: I agree - some people seem to have a math phobia. I have a kiddo who was like that. He got to eighth grade and said he'd had enough of math, that he wasn't going to be a math teacher so why should he spend time with algebra? This is the son who graduated college with a 4.0 average, so obviously he got past it. :D Thanks so much for stopping by and for your comment!

EnthusiasmMadame on June 15, 2014:

I can calculate most percentages off in my head. I loved math in school, however several family members including my daughter had a horrible time with math. I think people make it more often than it needs to be much of the time.

Susan Deppner (author) from Arkansas USA on June 07, 2014:

@shatabdi85: Lots of ways to do the calculation, shatabdi85, thanks for your contribution! I think the key is to not be afraid of math and to break it down into steps. Thanks so much for commenting!

shatabdi85 on June 06, 2014:

The method show over here is good & effective. Another easy method would be multiply the number with .7 to calculate 70% of a number.

Like (i) 70% of 80 is 80*.7=56

(ii) 70% of 25 is 25*.7=17.5

Susan Deppner (author) from Arkansas USA on June 01, 2014:

@TerriCarr: Great explanation of your method, which works on the same principle of breaking down the percentage into easy chunks. I agree about the teacher, too. My son reviewed algebra on YouTube and learned it so well, he CLEP'd all of his college math classes. What a great education we can get just from the right video teacher!

TerriCarr on June 01, 2014:

I use similar tricks to calculate things quickly. With the 70% off 250 problem, I would probably say, well 50% is 125, and I need to take off another 20 %, so I'd do 10% is 25, and times 2 is 50....so 125 - 50 = 75.

Love the Aussie accent and friendliness of the guy in the video. Just having a friendly, relaxed teacher would probably help a lot of math phobic people.

Susan Deppner (author) from Arkansas USA on May 29, 2014:

@asereht1970: Sometimes math does seem to take on a personality of its own! Glad you enjoyed the tip.

asereht1970 from Philippines on May 29, 2014:

Thank you for this wonderful tip. I guess I'm better with percentage than I am with fractions. Still, I'm not that good in Math. I don't like it and I believe it doesn't like me to.

Susan Deppner (author) from Arkansas USA on May 26, 2014:

@BenjaminFrancs: Percentages aren't so bad once you understand how they work. Then they're easy! Glad you learned to like them. Thanks so much for the great comment!

BenjaminFrancs on May 26, 2014:

Thanks, this wonderful. I had a problem with percentages until last semester of college. Now they are my favorite!

Susan Deppner (author) from Arkansas USA on May 23, 2014:

@Merrci: Thanks, Merrci. I hope so, too.

Merry Citarella from Oregon's Southern Coast on May 22, 2014:

What a great lens! Very interesting topic too. I'm always so surprised when people can't do 10 or 20%. Hope this helps many.

Susan Deppner (author) from Arkansas USA on May 22, 2014:

@Ruthi: I'm proud of you, Ruthi! I can, too, but not as fast as I used to do it!

Ruthi on May 22, 2014:

As much as I don't like math I am happy to report that I can calculate percentages in my pretty little head quite easily and correctly!