# Difference between revisions of "Difficulty"

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* Any one grinding of the hash stands the same chance of "winning" as any other. The numbers game is how many attempts your hardware can make per second. | * Any one grinding of the hash stands the same chance of "winning" as any other. The numbers game is how many attempts your hardware can make per second. | ||

* You need to know the difficulty (above) and your khash/sec rate (reported by the client). | * You need to know the difficulty (above) and your khash/sec rate (reported by the client). | ||

− | ** [[ | + | ** [[Mining Hardware Comparison]] has some stats that may help you predict what you could get. |

* Visit a calculator or perform the maths yourself, | * Visit a calculator or perform the maths yourself, | ||

** http://www.alloscomp.com/bitcoin/calculator.php | ** http://www.alloscomp.com/bitcoin/calculator.php |

## Revision as of 07:49, 26 December 2010

*See also: target*

## Contents

### What is "difficulty"?

Difficulty is a measure of how difficult it is to find a new block compared to the easiest it can ever be.

### How often does the difficulty change?

Every 2016 blocks.

### What is the formula for difficulty?

difficulty = maximum_target / current_target

(target is a 256 bit number)

### What is the current difficulty?

Current difficulty, as output by BitCoin's getDifficulty.

### What is the maximum difficulty?

The maximum difficulty is roughly: maximum_target / 1, which is a ridiculously huge number (about 2^224).

The actual maximum difficulty is when current_target=0, but we would not be able to calculate the difficulty if that happened. (fortunately it never will, so we're ok.)

### Can the difficulty go down?

Yes it can. See discussion in target.

### What is the minimum difficulty?

The minimum difficulty, when the target is at the maximum allowed value, is 1.

### How soon might I expect to generate a block?

(The eternal question.)

- Any one grinding of the hash stands the same chance of "winning" as any other. The numbers game is how many attempts your hardware can make per second.
- You need to know the difficulty (above) and your khash/sec rate (reported by the client).
- Mining Hardware Comparison has some stats that may help you predict what you could get.

- Visit a calculator or perform the maths yourself,
- Remember it's just probability! There are no guarantees you will win every N days.

*This article uses content from the old wiki. The list of contributors to the old page is available here.*