Bitcoin fees fluctuate constantly. Satoshi API analyzes mempool congestion in real time so you know whether to send now or wait a few hours and save up to 46%.
Bitcoin transaction fees are driven by supply and demand. Every block has roughly 1 MB of space (4 million weight units), and when more transactions compete for that space, fees rise. When fewer transactions are waiting, fees drop.
Daily patterns: Fees tend to dip during US nighttime hours (roughly 2 AM to 8 AM EST / 7 AM to 1 PM UTC). This is when US and European trading volume overlaps the least, and fewer businesses are batching payments.
Weekly patterns: Weekends typically see lower fees than weekdays. Tuesday through Thursday are historically the most expensive days to send Bitcoin, driven by business activity, exchange withdrawals, and institutional batching.
Post-halving dynamics: After each halving, miners earn fewer BTC per block. This can shift fee pressure as miners become more selective about which transactions to include. The 2024 halving also brought ordinals and inscriptions, which periodically flood the mempool and spike fees unpredictably.
Here is the problem with rules of thumb: they break. A single wave of inscription mints can spike fees at 3 AM on a Sunday. An exchange consolidating UTXOs can clear the mempool on a Wednesday afternoon. The only reliable approach is checking real-time mempool data before you send.
Three endpoints that turn raw mempool data into a send-or-wait decision.
The send-or-wait verdict engine. Analyzes fee spread, urgency premium, and congestion to tell you whether now is a good time to send or whether waiting will save you money. This is the single endpoint that answers "should I send Bitcoin right now?"
Three-tier fee recommendations: high priority (next block), medium (within 6 blocks, ~1 hour), and low (within 24 blocks, ~4 hours). Each tier shows the sat/vB rate your wallet should use. Pick the tier that matches your urgency.
Current mempool state: how many transactions are waiting, how much data is queued, and the minimum fee to get in. Use this to gauge overall network congestion before deciding when to broadcast.
A typical Bitcoin transaction with 2 inputs and 2 outputs (for example, sending to one address with change back to yourself) is approximately 141 virtual bytes.
During a congestion spike, the next-block fee rate might be 28 sat/vB. That means your transaction costs:
141 vB x 28 sat/vB = 3,948 sats (~$2.50)
Wait 2 hours for congestion to clear, and the fee rate drops to 12 sat/vB:
141 vB x 12 sat/vB = 1,692 sats (~$1.07)
That is a savings of 2,256 sats (~$1.43), or 57%, from one timing decision. During extreme congestion events (inscription waves, exchange runs), the spread between peak and trough can exceed 10x, turning a $15 fee into a $1.50 fee for the same transaction.
The /fees/landscape endpoint tells you when you are in a peak and when you are in a trough, so you do not have to guess.
AI agents that manage Bitcoin wallets or automate payments need programmatic access to fee timing decisions. The bitcoin-mcp server exposes Satoshi API's fee intelligence as MCP tools that any LLM can call.
# Install the MCP server pip install bitcoin-mcp # Zero config — auto-connects to Satoshi API if no local node
Once connected, an AI agent can ask natural-language questions and get structured answers:
# User prompt to Claude, ChatGPT, or any MCP-compatible agent: "Should I send bitcoin right now, or should I wait?" # The agent calls the get_fee_recommendation tool, which hits # /api/v1/fees/landscape under the hood, and responds: "Congestion is currently high (urgency premium 76.8%). I'd recommend waiting 1-2 hours. Medium priority at 8.2 sat/vB would save you 43% vs sending at next-block rates right now."
No prompt engineering required. The agent gets structured fee data and translates it into a human-readable recommendation. This is how autonomous Bitcoin agents make cost-optimal timing decisions.
Mempool.space is an excellent block explorer. It shows you the current fee rates, the mempool size, and projected blocks. But it answers a different question.
Mempool.space tells you what fees are right now. Satoshi API tells you whether you should send right now.
The difference matters. Seeing "15 sat/vB for next block" does not tell you whether 15 is high or low relative to the last few hours. It does not tell you the urgency premium you are paying. It does not score the congestion level or recommend waiting.
Satoshi API's /fees/landscape endpoint calculates the spread between high and low priority tiers, measures the urgency premium as a percentage, scores the congestion level, and returns a plain-language verdict: send now, or wait.
If you are building an application, Mempool.space's API gives you raw fee data. Satoshi API gives you a decision. Both have their place. If you want to display a fee chart, use Mempool. If you want to tell your users "wait 2 hours and save 46%", use Satoshi API.
How different tools help you decide when to send Bitcoin.
| Feature | Satoshi API | Mempool.space | Wallet Default |
|---|---|---|---|
| Send-or-wait verdict | Yes (plain-language recommendation) | No | No |
| Congestion scoring | Yes (low / moderate / high) | No | No |
| Fee trend context | Yes (spread, urgency premium, history) | Partial (mempool blocks view) | No |
| Real-time API | Yes (REST + SSE stream) | Yes (REST + WebSocket) | No |
| AI agent support | Yes (MCP server, structured responses) | No | No |
| Self-hostable | Yes (pip install, your node) | Yes (complex setup) | No |
| Cost | Free tier + self-host option | Free | Included with wallet |
Bitcoin fees tend to be lowest on weekends and during US nighttime hours (roughly 2 AM to 8 AM EST), when fewer transactions compete for block space. However, these patterns shift with network events like halvings, ordinals activity, and exchange batching schedules. The only reliable way to find the cheapest moment is to check real-time mempool data. Satoshi API's /fees/landscape endpoint gives you a live send-or-wait verdict based on current congestion.
Savings vary with network conditions, but waiting a few hours for lower congestion can reduce fees by 40-60%. A typical 141 vByte transaction at 28 sat/vB costs 3,948 sats. Wait for 12 sat/vB and the same transaction costs 1,692 sats — a 57% savings. During extreme congestion events, the difference can be even larger.
Yes. Historically, weekdays (especially Tuesday through Thursday) see higher fees due to business and exchange activity. Weekends tend to have lower fees as trading volume drops. But these are general trends, not rules — a single large batch of inscriptions or a protocol upgrade can spike fees on any day. Real-time data from a mempool API is more reliable than day-of-week heuristics.
You can check current Bitcoin fee rates using Satoshi API's /fees/recommended endpoint, which returns three priority tiers (high, medium, low) with sat/vB rates. For a send-or-wait decision, use the /fees/landscape endpoint which analyzes congestion and tells you whether now is a good time to send. Both endpoints are free to use and require no API key for GET requests.
Check real-time mempool congestion and get a send-or-wait verdict before your next Bitcoin transaction.