# Next Bitcoin Difficulty Adjustment Estimate

> Bitcoin difficulty adjustment estimate: blocks left until the next retarget, its projected date and the expected change from this epoch's block times.

Markdown copy of https://voltfincrypto.com/apps/bitcoin-difficulty-adjustment-estimate

**Question:** When is the next Bitcoin difficulty adjustment, and how big will it be?

- Kind: Dashboard in Voltfin Vantage
- Topic: [Bitcoin](https://voltfincrypto.com/topics/bitcoin)
- Chains: Bitcoin
- Status: Planned. The data is not published yet, so this page states no figure; each figure will open its receipt when it is.

The next Bitcoin difficulty adjustment happens at the end of the current epoch, and this dashboard counts the blocks left until it, projects its date and estimates how much difficulty will change if blocks keep arriving at this epoch's pace. The rules set the change: difficulty scales by how long the epoch's blocks took against a target of two weeks.

The estimate firms up as the epoch fills. Early in an epoch a few fast or slow blocks swing it widely; near the end it is close to exact, because most of the epoch's time is already on the chain. The dashboard draws the estimate as it moved through the epoch, names the block it was computed at and shows how past estimates compared with the changes that followed.

## Blueprint

### Next retarget

Blocks left, the projected date and the estimated change.

- **Blocks until the retarget** (blocks): Blocks between the latest block and the next retarget height.
- **Projected retarget date**: The projected time of the retarget block, from the epoch's average block interval so far.
- **Estimated change** (%): The difficulty change the epoch's pace so far implies, computed the way the rules will compute it at the retarget.
- **Average block time this epoch** (seconds): The average interval between blocks in the current epoch so far, against the ten-minute target.
- **Estimate through the epoch** (%): The estimated change recomputed at every block of the current epoch, which narrows as the epoch fills.
- **Block intervals this epoch** (seconds): Each block's time since the block before it in the current epoch, with the epoch's running average drawn across.

### Past retargets

Recent retargets and how the estimates compared with what happened.

- **Last retarget** (%): The difficulty change at the most recent retarget, against the epoch before it.
- **Midpoint estimate error** (%): How far the estimate made at each epoch's midpoint was from the actual change, averaged over the retargets in the period.
- **Change at each retarget** (%): The difficulty change at each retarget over the selected period.
- **Every retarget**: Each retarget with its height, date, new difficulty, change, the epoch's length in days and the estimate made at the epoch's midpoint.

Filters: Period (Last year, last four years or every retarget since the genesis block).

## How it will be measured

- The epoch starts at the last retarget height, a multiple of the epoch length; blocks left is the next retarget height minus the latest height from getblockchaininfo.
- The estimated change is the target timespan divided by the projected one, measured as the rules measure it from the epoch's first block to its last, and capped at a factor of four either way.
- The projected timespan and date extend the epoch's average block interval so far over the blocks left; both use header timestamps, which miners set within consensus limits.
- Each estimate is pinned to the block it was computed at, with its height and hash and the first block of the epoch it measures from.

## Data it needs

- `bitcoin_network_daily` (to build): Blocks, hashrate implied by difficulty, difficulty, fees, transaction counts, block weight and miner revenue (subsidy plus fees) per day.
- Source: getblockchaininfo at the chain head: blocks, difficulty and mediantime
- Source: Header timestamps of every block since the last retarget height
- Source: bits and difficulty from the first and latest headers of the epoch
- Source: The actual change at past retargets, to compare estimates with outcomes

## Questions

### What is the Bitcoin difficulty adjustment?

At the end of every epoch, about two weeks of blocks, each node recomputes the mining target from how long the epoch took. If blocks came faster than every ten minutes on average, difficulty rises; if slower, it falls, so block times return toward the target.

### How is the next difficulty adjustment estimated?

From the epoch so far: the average interval between its blocks is extended over the blocks left, and the projected epoch time is compared with the target time. The closer the epoch is to its end, the more accurate the estimate.

### How much can Bitcoin difficulty change at once?

The rules limit each retarget to a factor of four up or down. In practice changes are far smaller, because hashrate rarely moves that much within two weeks.

### Why do blocks come faster than every ten minutes?

When hashrate grows during an epoch, miners find blocks faster than the current difficulty expects. The next retarget raises difficulty to match, and until then blocks keep arriving early. Single intervals also vary widely, because finding a block is random.

### Does the difficulty adjustment affect fees?

Not directly. Faster blocks clear the mempool sooner and can lower fee rates for a while, and slower blocks do the opposite. The fees themselves are set by users bidding for block space, not by difficulty.

## Glossary

- **Retarget**: The recalculation of the mining target at the end of each epoch, which changes difficulty.
- **Epoch**: The fixed run of blocks between retargets, about two weeks at the ten-minute target.
- **Target**: The number a block's hash must fall below for the block to be valid. A lower target means a higher difficulty.
- **Median time past**: The median timestamp of the previous eleven blocks. A new block's timestamp must be later than it, which limits how far miners can set times back.

## Related apps

- [Bitcoin Hashrate and Mining Difficulty](https://voltfincrypto.com/apps/bitcoin-hashrate-difficulty)
- [Bitcoin Halving Countdown and Block Reward](https://voltfincrypto.com/apps/bitcoin-halving-countdown)
- [Bitcoin Mining Pools: Hashrate Share by Pool](https://voltfincrypto.com/apps/bitcoin-mining-pool-share)
- [Bitcoin Hashprice and Miner Revenue per Day](https://voltfincrypto.com/apps/bitcoin-miner-revenue-hashprice)
- [Bitcoin Transaction Fees and Mempool Tracker](https://voltfincrypto.com/apps/bitcoin-fees-mempool-tracker)
- [How Many Bitcoin Are Left to Mine: Supply and Issuance](https://voltfincrypto.com/apps/bitcoin-supply-left-to-mine)

Build it in Voltfin Studio: https://app.voltfincrypto.com/signup?next=%2F