🧠 Prompt Caching Savings Calculator
Estimate prompt-cache savings from reusable prefix tokens, cache hit rate, normal input price, cache-read price, request volume, and cache-write cost.
Calculate Prompt Caching Savings
What this prompt caching savings calculator calculates
Measure whether prompt caching is economically worthwhile for stable system prompts, long shared documents, or repeated tool schemas.
Caching works best when a large prompt prefix remains byte-for-byte stable and is reused often enough before expiration.
Prompt Caching Savings Calculator formula
Assumptions and limitations
The result is an engineering estimate based on the values entered. AI models, tokenizers, runtimes, accelerators, cloud services, and provider billing rules differ. Validate important decisions with measured data from the exact model, hardware, framework, and pricing plan you intend to use.
Worked example
For 100 million reusable tokens monthly, a normal rate of $2.50/M and cache-read rate of $0.25/M can save up to $225 before misses and cache-write charges.
How to use the result
Caching works best when a large prompt prefix remains byte-for-byte stable and is reused often enough before expiration.
- Start with representative production assumptions rather than best-case demos.
- Run a low, expected, and high scenario to understand the range.
- Record model version, pricing date, hardware, precision, and workload details.
- Replace assumptions with observed p50 and p95 measurements after testing.
Common mistakes to avoid
- Assuming every repeated request becomes a cache hit.
- Ignoring cache-write costs, expiration, or minimum cacheable prefix requirements.
- Changing timestamps, IDs, or formatting inside an otherwise reusable prefix.
Frequently asked questions
What is a prompt-cache hit?
A hit occurs when the provider can reuse a previously stored prompt prefix instead of processing it at the full input rate.
Why is cache-write pricing sometimes higher?
Some providers charge more to create the cache entry, offset by much lower read prices on later reuse.
Should dynamic user text be cached?
Usually only the stable prefix is cacheable; dynamic user content follows it and is billed normally.
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Methodology and privacy
This educational tool uses the formula and assumptions displayed on the page. Calculations run locally in your browser, and the page does not transmit the values you enter. Results are estimates rather than provider quotes, benchmark guarantees, financial advice, or capacity guarantees. Last methodology review: August 2, 2026.
Formula Explorer connections
Interpretation: This formula converts workload volume and unit rates into an operational cost or savings estimate. The result changes linearly with usage unless discounts, tiers or fixed charges are included. Assumption: Use rates from the same provider, model, region and billing period. Include retries, cached traffic, tool calls and overhead when they apply.