# Inscription Estimates To guarantee the safety of user funds, a watchtower/validator inscribes the state difference to bitcoin as a refundTx to safeguard user funds in case of liveness failure. This ensure the data availability of refund is guaranteed by the bitcoin blocks itself, ie. It uses bitcoin as a data availability layer to commit state difference transaction. **Some points to consider:** 1. Inscription size of RefundTx is largely depended on number of accounts in the system = number of refund outputs. 2. Every refund output in the refundTx adds \~30vbytes 3. The size of the compressed refundTx can change based on ratio of compression. 4. The 4 byte identifier reduces the output size by 26 bytes per address. 5. Estimated fees in USD changes with BTC price and network fee rate. Calculations below assumes 36 sats/byte for the calculations. BTC/USD price and current fee rate in the network are variable parameters and will change fee in USD numbers. 6. This document assumes a bull case for Bitcoin. Assumptions may be different for a bear case. **What we don’t consider:** 1\. Consuming more than half the block space by other L2 projects will create fee pressure in the system, leading to much higher sats/byte | Number of refund Output | Inscription Size (vBytes) | Fee in Sats @
36 sats/byte | Fee in USD 
@ BTC = \~$65,500 | Inscription Size (bytes) with 4 byte identifier | Fee in Sats with 4 byte identifier @ 36 sats/byte | Fee in USD with 4 byte identifier @ BTC = \~$65,500 | Fees in USD with 4 byte identifier @ BTC = $100,000 , 36 sats/byte | Fees in USD with 4 byte identifier @ BTC = $100,000, 50 sats/byte | | ----------------------- | ------------------------- | -------------------------- | ----------------------------- | ----------------------------------------------- | ------------------------------------------------- | --------------------------------------------------- | ------------------------------------------------------------------ | ----------------------------------------------------------------- | | 1 | 600 | 21600 | 14 | 585 | 21060 | 14 | 21 | 29 | | 100 | 2760 | 99360 | 65 | 2748 | 98938 | 53 | 99 | 137 | | 250 | 6015 | 216540 | 142 | 4768 | 171648 | 113 | 171 | 239 | | 500 | 12015 | 432540 | 284 | 8970 | 322920 | 212 | 323 | 448 | | 750 | 18866 | 679176 | 445 | 13170 | 474120 | 311 | 474 | 658 | | 1000 | 24291 | 874476 | 572 | 17370 | 625320 | 411 | 625 | 868 | For \~ 100 bitcoin blocks a day, we assume 100 inscriptions committing a state difference. Per day cost of inscriptions for 100 inscriptions a day \~ $ 411 \* 100 = $41,100 Per month cost if BTC/USD price remains the same = $41,100 \*30 = $1,233,000 6 month estimate if price remains the same = $7,398,000 6 month estimate with BTC @ $100k and fee rate @ 36 sats/byte = $11,255,760 6 month estimate if fee rate rises to 50 sats/byte with BTC @100k = $15,633,000 --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.twilight.org/boomerang/inscription-estimates.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.