What is maximum limit of GAS in a smart contract

Question

Can you please explain the concept GAS in smart contract properly if possible with example. And what is the max limit of GAS in a contract?

It is clear if i use more gas i have to pay more...so where i can get that actual calculations.

Answer 1

There are many good YouTube presentations on this topic. I recommend one by Joseph Chow from ConsenSys. Watch it here: "Ethereum, gas, fuel, and fee" https://youtu.be/dd-ajiMl4HY

A contract call can take all gas per block if the contract tx is lucky enough to be the only one tx in a block or you mine a block yourself . The current gas limit can be checked on the network stats page. https://ethstats.net/

Answer 2

You can use the following Web3 JS function to estimate Gas before making any smart contract function call -

https://github.com/ethereum/wiki/wiki/JavaScript-API#web3ethestimategas

Also, the Gas Limit is defined in the genesis.json file, before initializing the genesis block.

You can take a look at this link to understand these concepts better -

https://souptacular.gitbooks.io/ethereum-tutorials-and-tips-by-hudson/content/private-chain.html