Is there a significant difference between chess calculation over the board vs online?

?

no i dont think so

on chess.com you have arrows on otb you dont

not a significant difference

Yes.

If you use same time control OTB as you do online, there should be no significant difference.

If you mean that you play long games OTB, the calculation does have significant differences, in the sense that you'll have to calculate not only your strategy, but also your opponent's strategy.

I have found out that when playing blitz or rapid online, the games oftentimes are decided by who will initiate his/her attack first. It is usually better to choose a faster path to attack than to form a more balanced position.

I haven't noticed a difference. In both settings one must calculate your own plans and your opponents, games at my level are decided by who outplays the other, usually by finding a better plan through more accurate calculation and evaluation of the position.

only visionaly

It is best to play the position according to the demands of the position, whether blitz or OTB.

lol Nothing about on line chess truly matters. your online calculations are trivial and inexpensive. Your OTB calculations have a round trip, entry fee, meals, rating points, and even lodging on the line.

Online calculations are on a screen that you click a mouse for... OTB you must physically move the piece, manually operate the clock, and keep score of the game. There's also that pesky touch move rule!

As mentioned earlier, at 5 minutes or less, it's about the same, but once the clocks are set to 30 minutes, online has no comparison to OTB.

There's also no bonus points, no norms, no categories, and very few cash prizes on line!!

OTB has less cheating as well!

Nope. About 1/4 of my online losses are due to being flagged, even though i have a big positional advantage.

I find OTB much easier than online because I see the complexities better due to stereoscopic vision.

I know many young players find the opposite true.

Choosing openings in blitz that lead to sharp or attacking positions is fine. But playing positions in a manner that is at odds with the demands of the positions is an impediment to improvement.

Playing blitz is for fun, NOT for improvement. I never heard any serious player advise people to improve their skills via blitz.

You may be a stronger player but i have played 20,000 + blitz online, vs your've played less than 2,000. I don't think you understand online blitz games more than I do.

My first ONLINE blitz game was in 1993. Yes, that is when the first chess server came online. Blitz is a part of how many strong players acquired their ability. It is not a substitute for slow chess, learning to calculate variations, and the study of endgames, tactics, and openings. But blitz gives you a chance to put the ideas you study into action much sooner and in more varied ways than slow chess play. But that assumes you try to handle the positions in accord with their demands, trying to put into action what you learn in your studies.

You are entitled to your opinion and i have no intention to debate you. I do find an old thread discussing this topic. See below for the link. You may want to persuade all the responders there. I am out.

GMs and Blitz

I hope you are not suggesting that GMs routinely play game/5 time controls by handling positions in ways that are at odds with the demands of the positions.

Playing on board is better in my opining because after some time pain from computer screen will make you love board chess.

Online, many people dont play with increment, so this can make a difference in OTB, since when there's increment, its harder to time someone out. However, you also have to move the pieces physically then touch the clock, so it is easier to get timed out in some situations. For calculating, for some people, it may be easier to see all the pieces on the screen. In OTB, if you put your head down on the table, the pieces will hide each other. However, this shouldn't be much of a problem.
Rapid OTB is similar to Chess.com rapid, and blitz OTB is similar to chess.com blitz, except the time aspect also involves hitting the clock fast. 
I disagree with @MyBrainNeedsOil about how rapid and blitz games are decided about who attacks first. An initiative is a great advantage to have, but if the position is balanced as in one side has an initiative, and the other side has something else in return, then we cant say that the initiative will win more often in rapid as compared to classical.