How to Use This Tool
Weight measured candidate file sizes by audience mix and cache-miss assumptions. Estimate responsive-image transfer from page views, mobile share, measured mobile and desktop bytes and a cache-miss percentage.
The decision this tool supports
One desktop image weight multiplied by all traffic overstates mobile transfer, while ignoring cache misses can overstate every repeat view. This page keeps the decision bounded to estimated image transfer and the supporting outputs shown beside it. Responsive Transfer does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The Responsive Transfer calculation uses Page views, Mobile view share, Measured mobile image size, Measured desktop image size, Transfer-causing view share. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing Responsive Transfer scopes can produce a plausible number with the wrong meaning.
- Page views is entered in views.
- Mobile view share is entered in %.
- Measured mobile image size is entered in KB/view.
- Measured desktop image size is entered in KB/view.
- Transfer-causing view share is entered in %.
Formula and worked check
Transfer GB = views × device share × measured KB per view × transfer-causing share ÷ 1,000,000, summed across device scenarios. At 100,000 views, 70% mobile, 180 versus 420 KB and 35% transfer-causing views, the model totals 9.66 GB. The Responsive Transfer default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of estimated image transfer still matches the stated relationship.
How to interpret the result
Replace candidate sizes with a network trace from representative viewport and DPR combinations, then compare the weighted result with CDN analytics. The additional Responsive Transfer outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- KB uses decimal 1,000-byte units.
- Each scenario downloads the entered image bytes once when transfer occurs.
- Mobile share is mutually exclusive with desktop share.
Save the Responsive Transfer input values and date with any material decision. A later Responsive Transfer rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
It excludes DPR subgroups, Save-Data, preload behavior, format negotiation, cache eviction, header bytes, compression variance and bot traffic. Responsive Transfer is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The Responsive Transfer definition or rule was checked against MDN Web Docs — TextEncoder on 2026-08-26. Recheck MDN Web Docs — TextEncoder when a specification or policy behind Responsive Transfer can change. Responsive Transfer arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- MDN Web Docs — TextEncoder (checked 2026-08-26)
Model assumptions
- KB uses decimal 1,000-byte units.
- Each scenario downloads the entered image bytes once when transfer occurs.
- Mobile share is mutually exclusive with desktop share.
- It excludes DPR subgroups, Save-Data, preload behavior, format negotiation, cache eviction, header bytes, compression variance and bot traffic.
