I’ve looked at a number of calculators for iOS that run on the iPhone, iPod Touch and iPad and have a few that I really like. In my list I will also include a few others that you may not use all of the time but when you need them they are great as well.

Calculator

The calculator application that comes on the iPhone, iPod Touch or the iPad is actually quite good. In vertical mode it is a nice basic calculator and in horizontal mode it becomes a great scientific calculator. You can copy and paste the answer if you need it to another application. For a while this was the calculator I used all of the time.

Universal App that came with your iPhone or iPad (Free)

PCalc RPN Calculator

This is my favorite calculator to replace the out of the box Calculator app from Apple. Don’t let the name turn you away. While it is a great RPN calculator you don’t need to use it that way.

If you don’t know what RPN or Reverse Polish Notation is you may want to check it out. HP makes a number of calculators that use RPN. I had an HP-41CV calculator in high school and college and preferred it over a standard calculator. It also had the advantage that anyone who borrowed your calculator usually handed it back to you rather quickly since they didn’t know how to use it. Once you learn the input it really is faster since there is no need for parentheses. I actually don’t use RPN on a regular basis anymore since most calculators you pick up don’t work that way. I use PCalc in the standard mode.

The settings in PCalc make it possible to change it’s look to make it your own. Here are the areas you can change:

• RPN Mode – turn it on or leave it off. I expect the majority will leave it off but give it a try – you might prefer it!
• Multiple Memories – if you need it this is great. If you are fine with one then leave it off since it adds extra key strokes
• Thousand Separators – I like it on to make the numbers easier to read.
• Number of Decimals – You get a slider to choose number of decimal along with the type of notation – normal, engineering or scientific.
• Themes – choose you favorite color theme from among the 10 they offer. I use Twilight but there is surely one you will like.
• Digits – choose the digit style and color for the display. I like being able to choose a smooth easy to read look. Some calculators go out of their way to look like real calculator displays. The technology defined that look and I don’t want it that way if I have a choice.
• Display – choose the number of lines you want to see on the display. You can even choose a different number of lines in vertical and horizontal.
• Layout – The key layouts can be basic to keep larger keys but also include an engineering layout for landscape which I use or even a programming layout for hex, octal and binary.
• Key Click – turn on the key click and choose your favorite sound.
• Advanced Settings – there are a number of advanced settings that you can customize even further. I have all of mine set to the defaults.

When you use the calculator, there are number of features that are nice that aren’t in the Apple Calculator. For basic feedback, the key clicks are nice to have. You also get a visual feedback when you press a key. Similar to the keyboard on the iPhone or iPad, when you press a number you will see it enlarged next to your finger. You would think Apple’s calculator would do this since the standard keyboard does but it doesn’t. One of the bigger annoyances on the Apple calculator is the lack of a backspace key. If you enter a digit wrong you have to clear and type again. PCalc provides a backspace key to let you correct a single digit. On a small device like the iPhone or iPod this is very helpful.

Conversions are one of those things that you go blank on when somebody asks you to do it. How many teaspoons in a tablespoon? How many kilometers in a mile? PCalc does a wide range of conversions whenever you need them. There are 16 categories of conversions. What you need is likely there.

Want to check what you keyed in or see the answer to a previous calculation? The tape is just what you are looking for. You can copy the tape to take it to another app or you can even email it.

Need to remember the speed of light or the mass of the moon? I’m sure you don’t need this button since they are just sitting on the tip of your tongue. If you want to double check, there are six categories of constants for your reference. There is probably a couple you don’t remember.

All of the extra features are nice, however in the end, this calculator just feels right when you use it.

Universal App for both iPhone and iPad ($9.99)

Lite version available (Free)

INCHcalc+

This calculator isn’t for everybody but if you work with architectural prints like I do then you will want a construction calculator that does feet – inches – sixteenths calculations. When apps first became available on the iPhone platform this is an app that I kept waiting for. This was the first app on the store that did what I needed. Today there are many more choices including versions of the popular Construction Master calculators from Calculated Industries. INCHcalc+ has always met my needs and so I have had no reason to seek out one of the other solutions. Vertical view presents a basic input with bigger keys while the horizontal view provides many more conversions including pitch, rise and run calculations. My only complaint – I wish the backspace key was on both screens and not just the horizontal view.

Universal App for both iPhone and iPad ($4.99)

Graphing Calculator

When my daughter started Algebra II, we found that even these calculators don’t quite cut it for certain situations. Graphing calculators are standard equipment in high school math. I have to admit I don’t really like these stand alone calculators for graphing. The interface is so much harder to use, the screens are too small and typically black on gray. A computer or something like this app is much quicker and easier to understand. It can display up to four graphs and has a trace mode which can snap to intersections, minimums and maximums with a touch of your finger. These are usually the answers you are looking for. There is also a table view that displays all of the points based upon whatever increment you choose. This app does not let you enter a table of data and do best fit curves. If you need that this isn’t your app.

I don’t particularly like this app as my everyday calculator but for graphs it is great. The developer has even added a video out feature which would be great in a classroom situation. Eventually my daughter and I determined that she would need a TI graphing calculator since you can’t use anything else on standardized tests such as the PSAT or the SAT. Learning how to use them is required at least for the near future. I find she always chooses her iPhone first as a calculator and the TI as a last resort.

Graphing Calculator for iPhone ($1.99)

Graphing Calculator HD for iPad ($1.99)

WolframAlpha

Now this is an app that is difficult to explain. The app connects to the WolframAlpha web site for it’s answers, therefore, an internet connection is required. The goal of the site is to provide a single source that can be relied on by everyone for definitive answers to factual queries. While it is excellent at mathematics it is also able to give you facts on a city or your first name. Try giving it a couple of stocks to compare or a chemical formula. The data that is pulled together is pretty amazing.

For mathematics, it can do things no ordinary calculator can do. Give it a quadratic equation and it will solve it and graph it. Have a calculus integral or derivative? WolframAlpha will solve it and graph that as well. In seconds. That’s the part that got a reaction from my son as he noted how long that took him to do by hand! While it may be hard to explain this app, when you see what it can do you will agree it is a great app to have for $0.99.

Speaking of price, this app was hard to recommend when it first came out. The price tag was $50. Yes the decimal place is correct and yes the web site was free. Today the price is $0.99 and I can recommend it highly. The value of the app over using Safari is worth the buck but you can just use Safari on your iPhone or iPad.

Oh and don’t expect a teacher to let you use this during a test. It would be better than cheating off your neighbor!

Universal App for both iPhone and iPad ($0.99)

SpaceTime

This app does what Graphing Calculator does and much more. This app can do more than any other calculator app on the list without requiring an internet connection like WolframAlpha. My biggest problem with the program is the entry. To accomplish the scope of problems it can handle will require you to learn the syntax. Once you get the hang of it the entry isn’t hard but there is a learning curve here. The benefits come with the output and the types of problems it can solve. It can handle integrals and derivatives for calculus as well as those quadratic equations. Graphs can be viewed and traced while a table is created that can be reviewed. This impressive program can handle all of it but it won’t be your day to day calculator.

SpaceTime for iPhone ($9.99 on sale; normally $19.99)

SpaceTime for iPad ($9.99 on sale; normally $19.99)

Final Thoughts

These certainly aren’t the only calculator apps available for your iPhone or iPad. If you need special calculators for a certain situation there is likely one for you. If you have a favorite real calculator, try searching and see if someone has replicated the look and created an app. I have looked at other calculator apps and many don’t quite get the interface right. This list of apps has done a good job with both features and usability. If you have a favorite, let me know. I’d love to check it out.