When Is the Cheapest Time to Send Bitcoin? Read the Mempool (2026)

Two clocks run inside every swap. One measures the network fee you pay to get BTC into the order; the other measures the rate the pool gives you on the way out. The rate is quoted before you commit and locks when the order is created — that part is fixed. The fee is an auction for block space, and it changes hour by hour. At the time of writing (2026-10-15, around 06:00 UTC) that auction was quiet: mempool.space showed 80,350 pending transactions holding 39.69 MvB of block space, with recommended rates of 2 sat/vB at the fastest tier and 1 sat/vB for the half-hour, hour and economy tiers alike. Block 971,519, mined at 05:51 UTC, had cleared 6,261 transactions at a median of 0.30 sat/vB. Every rate in this article is as of writing; live quotes on the exchange page are the ones that count. (how Monero fees work)

A Bitcoin fee is a bid on vbytes, not a price list. Block space is measured in virtual bytes, and your transaction claims some of it: a native SegWit payment with one input and two outputs is roughly 141 vB, while a legacy one is closer to 226 vB — the same money, 60% more block space. Multiply your size by the rate you are willing to bid and you get the fee. Because Bitcoin Core's default relay floor is 1 sat/vB, that is the practical bottom under normal conditions. Today's data shows how wide the bids really are: the next projected block has a median of 1.00 sat/vB, but the top of its range reaches 100.3 sat/vB. Someone is paying a hundred times the going rate for the same block — almost always a wallet default or an exchange withdrawal setting, never a market requirement. (how Monero fees work)

Reading the mempool takes one minute. Open mempool.space and look at two things. First the five recommended tiers — fastest, half-hour, hour, economy, minimum; today they read 2 / 1 / 1 / 1 / 1 sat/vB. Then the block projection, which estimates what each upcoming block is actually going to clear at: read the median, not the average, because a single overpayer drags the average up. The third number is queue depth: 39.69 MvB waiting, divided by roughly 1 MvB of vbytes per block, is about 40 blocks, or six to seven hours of work — but the tail of that queue is bidding 0.2 to 0.3 sat/vB, so a 1 sat/vB bid does not sit behind it. Today the honest answer to when to send is: now, at 1 sat/vB, and there is no reason to pay the 2 sat/vB fastest tier.

Convert sat/vB into dollars before deciding. At the BTC price on our price feed this morning ($80,616.72), a 141 vB native-SegWit spend costs 141 sat = 0.00000141 BTC at 1 sat/vB, which is about $0.11; the same transaction costs $0.23 at 2 sat/vB, $1.14 at 10, $3.41 at 30 and $5.68 at 50. A legacy 226 vB spend is roughly 60% more: $0.18 at 1 sat/vB, $9.11 at 50. On a $100 swap that spans 0.1% to 5.7% of the amount — which is the entire story of fee timing. The floor today is 1 sat/vB, so the cheapest hour is any hour where the first projected block's median sits at that floor, and the most expensive hour is the one where you let an unread wallet default place your bid for you. (how Monero fees work)

The order clock is not the chain clock. Creating an order gives you a deposit address, a 30-minute deposit window and a rate locked at creation. The transaction then moves through four visible states: waiting_deposit, confirming, settling, paid. A fee that makes the next block clears all four in minutes. A fee that undercuts what the auction is clearing at can sit in the mempool long enough that the deposit arrives after the window — at which point the order expires and whatever lands is handled as a late deposit, refunded to the refund address you set, rather than swapped at the rate you locked. Our own sweep keeps re-checking the provider for up to six hours after a local expiry so a late deposit is not silently recorded as cancelled, but being caught is not the same as getting your locked rate. Trading ten cents of fee against that risk is a bad trade. (recovering misdirected funds)

The Monero leg has no auction to time. XMR's fee is dynamic but there is no bidding war. A public Monero node today (height 3,784,374) estimated 20,000 atomic units per kB, i.e. 0.00002 XMR per kB; its transaction pool held just 63 pending transactions, and the median block used 300 kB of a 600 kB weight limit. A typical two-input, two-output transaction weighs roughly 2.2 kB, so the fee lands near 0.00004 XMR — about two cents at today's XMR price. Monero wallets expose higher-priority multipliers (1x, 4x, 16x, 200x) because paying for speed is possible, but you rarely need them. Spend your attention on the Bitcoin leg; the XMR payout is cheap by default. (how Monero fees work)

Size beats timing, measurably. Pulling BTC→XMR quotes this morning, the rate depended heavily on order size: 0.0002 BTC quoted 100.62 XMR/BTC, 0.0005 quoted 129.52, 0.001 quoted 139.16, 0.002 quoted 143.93, 0.01 quoted 147.77, 0.05 quoted 148.55 and 0.2 quoted 148.66. The smallest size gets about 32% less per BTC than the largest — on a $16 order that is a gap of roughly $5, about fifty times the on-chain fee we have been optimizing. The pair minimum today was 0.00017225 BTC (about $13.89) with a maximum of 2.1850672 BTC; USDT-TRC20→XMR started at 19.16 USDT and 100 USDT quoted 0.16535023 XMR. Choose the order size first, the hour second. (XMR to USDT exit)

The checklist, in order. Look at the mempool before you create the order: the five tiers plus the first projected block's median. Set that median as a custom fee — 1 sat/vB today — instead of accepting the wallet's fast default. Prefer a native SegWit wallet: 141 vB instead of 226. Consolidating many small UTXOs? Wait for a floor-rate window, because a five-input spend can be two to three times the vbytes. Already sent too low? Raise it with RBF if the transaction signalled BIP125 replaceability; if it did not, use CPFP from the receiving side. If the deposit misses the 30-minute window, do not send a second payment to the same order — a second send is simply a second deposit, while a late arrival is already tracked and handled through the refund path. And low fees buy no privacy: your fee choice is public either way. Timing saves cents; wallet choice and order size save dollars. (how Monero fees work)