I mean, sometimes bitcoin network is overloaded and transactions goes too slow. Where I can see this info in numbers ?
I suppose you're talking about the unconfirmed transactions in the mempool...
This site should give you an idear :
https://blockchain.info/unconfirmed-transactionsMaybe this is what I want, but how can I estimate bitcoin load using info given on that page ?
Some clarification of what I want: 500 bytes transaction with 0.0001 btc fee was processed in 10 minutes when system was 10% loaded
and 500 bytes transaction with 0.0001 btc fee was processed in 2 hours when system was 90% loaded.
I want to go to some page and see "Bitcoin network is loaded on 90%", then I set fee 0.0002 for 500 byte transaction..
Not exactly what you asked for, but you could use this page:
https://bitcoinfees.21.co/It gives you an estimation of how much satoshi's per byte you should add to get into the next x blocks on average.
Do be carefull: it's up to the miner if he adds your tx to a block or not. He can chose to add a tx with allmost no fees to a block before adding a tx with really high fees per byte, but usually he'll add the ones with the highest satoshi/byte fee
better.
There is no such thing as the network being x% full. It has no storage capacity. Think of it as a queue. Cointape.com will show you how long you transaction should take based on the past hour and the mempool.