Write down what was actually observed
A best bid and best ask describe a quoted snapshot. An average fill price summarises transactions in your supplied execution records. Before comparing them, record the venue, instrument, quote currency, observation time and quantity scope. A matching short symbol alone does not make the observations interchangeable.
The cited market-data schema separates trade price and quantity fields from bid/ask quote fields. It is a schema illustration, not a live market sample. Save the endpoint or export type so a later reader can tell whether a row describes a quote, a trade or your own calculation.
Calculate a named benchmark from fictional inputs
Suppose an invented USD quote has bid 99 and ask 101 per unit. Its arithmetic midpoint is 100 and its quoted spread is 2. A separate fictional fill set contains 0.4 units at 101 and 0.6 units at 102. The total quantity is 1 and the quantity-weighted average is 101.6.
Against that particular midpoint, the fill average is 1.6 USD per unit higher, or 1.6% of 100. Preserve the name of the benchmark when reporting the difference. Do not rename it a net trading cost: the example has not supplied commissions, funding, rebates or the timing evidence needed to evaluate execution quality.
| Supplied item | Fictional value | Meaning |
|---|---|---|
| Quote midpoint | 100 USD/unit | Arithmetic midpoint of 99/101 |
| Fill average | 101.6 USD/unit | (0.4×101+0.6×102)/1 |
| Difference from that midpoint | 1.6 USD/unit | A comparison, not proof of slippage cause |
Do not merge a SGD display with a USD execution
A Singapore reader may save a platform display in SGD while an execution export labels its prices in USD or a quote token. The currency label is part of the observation. Comparing the bare numbers would produce an unexplained difference even if both files are internally correct.
If you perform a separate FX conversion, retain its rate direction, timestamp and evidence. Do not treat that analytical conversion as the venue's quoted book. A daily currency rate and an execution-time rate are different observations; without the required conversion evidence, withhold the monetary comparison.
A contradictory snapshot should not be silently repaired
If the supplied ask is below the supplied bid, preserve both values and their observation references. You may have joined different instants, instruments or currencies, or observed a condition that requires venue-specific interpretation. Taking an absolute spread or swapping the labels would hide the discrepancy rather than resolve it.
The fill average also requires a non-zero summed quantity with a defined unit. Missing quantities should not become one-unit trades merely to make an average available. If the source includes cancelled or corrected fills, retain those states and decide which rows belong in the comparison under an explicit rule. A transparent withheld result is more useful than a precise-looking number built from inconsistent rows.
Keep time and displayed size beside the price
A snapshot saved before the fills does not establish the order book at each fill. Its displayed size also does not prove that your whole quantity was available at the best ask. Keep snapshot time, fill times and quoted quantities rather than explaining every difference as poor execution.
Use separate output columns for the benchmark value, the fill average, the currency match and unresolved timing or size gaps. No side, maker role or fee schedule is inferred from the difference. The result is a reproducible record comparison, not a recommendation to enter, cancel or route an order.
The optional link below leads to this site's separate crypto signals and Telegram updates offer. The record method is usable without that offer. It does not independently verify the offer, establish country eligibility or turn the teaching example into an actual transaction.
Primary sources and scope
- Binance Developer Docs: Spot market data
Illustrative public trade and quoted bid/ask fields; no live data or platform eligibility established. Checked 2026-10-21.