Seems like there's no thread comparing scientific calculators. That was one of my first priorities upon getting my droid X. Here are some notes on some I tried. But first, my criteria--I was looking for: Most commonly used functions on a single screen Multi-line display showing calculation and result. Complex numbers would be great, but not essential...since none of the first ones I found do that, I'll save ones that do that for another post Mathdroid, my favorite so far. Has a numpad and basic operators on the bottom, the 5 most recent calculations at the top (and you can scroll back for more), and two rows of scientific buttons in the middle. My only complaint is that there are two sets of those buttons and a toggle button to switch sets. I constantly need to switch, as pi is in the secondary set, whereas trig, log, ^ and sqrt are in the main set. There are additional functions, such as, for example, BitShiftRight, that you can get by typing on the keyboard, but that aren't available with buttons. You can also assign values to variable names, (e.g. a=12) using the keyboard. No graphing, solving equations, etc. HandyCalc This seems very popular and with good reason. Nice interface and powerful. Has all the bells and whistles, like graphing, solving equations, etc. The main screen has the number pad plus x^2, and sqrt, and EE (exponential notation); a "shift" button gets you to all the usual scienfitic stuff, like pi, trig, and x^y. That doesn't quite satisfy my ideal that it have everything on one screen, but it's close. After you hit pi, for example, on the "shift" screen, it automatically goes back to the numpad screen (for better or worse...probably better). One thing I really like is that it displays what you enter in real math notation, for example a symbol for pi instead of the letters p and i, and exponentiation using superscripts rather than ^. CalcBuddy Pretty nice. If you are entering a long expression, it displays the result so far before you hit enter--e.g., if you enter 5x5x5, it will display 25 when you've gotten as far as 5x5. Sadly for me, the commonly used buttons are spread over three pages, and I'm not going to want to keep moving between them. Otherwise very nice, although the instant-result feature takes a little getting used to. Stock Calculator on my Droid X. Just for reference--it has trig, pi, e, ^, ! and sqrt, but to get those you need to select the "advanced panel" from the menu, at which point the numpad goes away. Ridiculous--useful only in a pinch or for basic calculations. Calc+ There's a free and a paid version. I tried only the free. This has an attractive screen with colors that remind me of my dad's 1973 TI SR-10. And in landscape mode, it has most of the frequently-used buttons on one screen. Sadly though, it's missing input in exponential notation, the feature that prompted my dad to spend $100+ on the SR-10. It's also missing multiple-line display, and it doesn't even display the whole calculation on one line as you enter it--if you enter 1+2=, the 1 disappears from the screen when you hit +. Paid version adds unit conversions. Uninstalled. HowlCalc_lite This looked good but I lost interest when I tried to calculate 10^2 by typing 10 then hitting the "^2" key. It displayed 10pow2(. Apparently I'm supposed to hit the ^2 button and then 10. When I do that, it displays pow2(10, and I can hit return and get 100, without ). But I have no interest in learning its quirks when there are better options. Uninstalled.