How do you know how much your exploration data is worth?

[Hasaf]

I see people saying that they have X amount of exploration data. Where are they seeing the value of the exploration data on-board?

 

[tafkabb]

They guess. There's no way of knowing until you cash it in.

 

[TERMINATRIXXX]

You can calculate it, depending you know and count what you have discovered/scanned.

There are additional rewards for using the Detailed Surface Scanner and Discovered first scans.

http://elite-dangerous.wikia.com/wiki/Explorer

 

[XrayRomeoAlpha]

sell it if you want to know.
its the only way to be sure

 

[mung0]

People are guesstimating on how much & what they've been scanning on a trip.

 

[Mr Cynical]

As stated it's all guesstimated but it's worthless until you actually hand it in.
Get blown up before that and it's all gone.

Some people have had issues with hyperspace dumping them into a star's ejection cone and then frying while not being able to escape. If you get blowed up due to a game bug you can report it and ask FD if they can reinstate your CMDR's prior state (or compensate the credits)