I guess you know the answer, but let me try to answer this with my words (hope my english is okay).

The Coin-/ Mining-Difficulty will be calculated for

**BitCoin** as followed:

1 Block

**should** be found every 10 minutes.

After (every) 2016 blocks the BitCoin-Network will check how long it took to find these 2016 blocks.

Let's say the BitCoin-Project has started a few weeks ago and you are the only BitCoin-Miner and your machine has a Hashrate of 1 GH/s.

The difficulty is

139.70 at this moment, so how long would the network (means you, cause you are the only miner) need to find 2016 blocks?

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You start your machine with

**1 GH/s** Hashing-Power, the result will be (frist 2016 blocks):

Check-Intervall = 2016 blocks

Hashrate = 1,000,000,000 Hashes/s

Diff = 139.70

Time per Block = (Diff * (2^32)) / Hashrate

Time per Block = (139.70 * (2^32)) / 1,000,000,000

Time per Block = 600.0069313 seconds

Time for 2016 Blocks = Time per Block * Check-Intervall

Time for 2016 Blocks = 600.0069313 * 2016

Time for 2016 Blocks = 1,209,613.973 seconds

Time for 2016 Blocks = 14 days (1,209,613.973 / 60 / 60 / 24; rounded)

If it would be exact 14 days, the BitCoin-Network will NOT change the difficulty (so the next 2016 blocks, the difficulty will still 139.70).

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But if you start now 2 machines with

**2 GH/s** Hashing-Power the result will be (seconds 2016 blocks):

Check-Intervall = 2016 blocks

Hashrate = 2,000,000,000 Hashes/s

Diff = 139.70

Time per Block = (Diff * (2^32)) / Hashrate

Time per Block = (139.70 * (2^32)) / 2,000,000,000

Time per Block = 300.0034656 seconds

Time for 2016 Blocks = Time per Block * Check-Intervall

Time for 2016 Blocks = 300.0034656 * 2016

Time for 2016 Blocks = 604,806.9867 seconds

Time for 2016 Blocks = 7 days (604,806.9867 / 60 / 60 / 24; rounded)

So the network (your 2 machines) solved the blocks

**too fast**, after only 7 days you found the 2016 blocks, the BitCoin-Network will now increase the difficulty by

**100%**.

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So if you still have your 2 machines with

**2 GH/s** Hashing-Power the result will be (third 2016 blocks):

Check-Intervall = 2016 blocks

Hashrate = 2,000,000,000 Hashes/s

Diff = LastDiff + Increase

Diff = 139.70 + 100%

Diff = 279.40

Time per Block = (Diff * (2^32)) / Hashrate

Time per Block = (279.40 * (2^32)) / 2,000,000,000

Time per Block = 600.0069313 seconds

Time for 2016 Blocks = Time per Block * Check-Intervall

Time for 2016 Blocks = 600.0069313 * 2016

Time for 2016 Blocks = 1,209,613.973 seconds

Time for 2016 Blocks = 14 days (1,209,613.973 / 60 / 60 / 24; rounded)

Now you

**should** solve the 2016 block in 14 days. Because there are many Miners the overall network hashrate (at this moment 6,506,281,489 GH/s) will change everytime, so you can calculate the next difficulty at the current moment, but this will change after a few seconds.

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Summary:

+10% Hashing-Power (overall in network) since last Diff-Set = +10% Difficulty at next set (after reaching the next 2016 blocks)

-10% Hashing-Power (overall in network) since last Diff-Set = -10% Difficulty at next set (after reaching the next 2016 blocks)

But the difficulty will only change every 2016 blocks (for BitCoin), which means after the last difficulty set, the difficulty will NOT change until the next 2016 blocks will be reached.

Maybe this helps someone

Greetings

Paul