Inference optimization

Prompt Caching Break-Even Calculator

Calculate whether cache writes, reads, misses, and invalidations make prompt caching worthwhile.

Your scenario

Adjust the assumptions. Results update instantly.

Model

Cacheable prefix tokens

tokens

Stable system prompt, tools, examples, or document context.

Fresh input tokens

tokens

Request-specific content that cannot be served from cache.

Output tokens

tokens

Average generated response per request.

Requests per hour

requests

Average request volume during active periods.

Active hours per month

hours

Hours during which the workload generates requests.

Expected cache-hit rate

Share of requests that reuse a valid cached prefix.

Cache-write price multiplier

Write cost relative to normal input pricing when provider data is unavailable.

Cache-read price multiplier

Read cost relative to normal input pricing when provider data is unavailable.

Methodology

How this calculator works

Price the repeated prefix at normal input rates without caching.

Price hits at cache-read rates and misses at cache-write rates.

Compare both scenarios and calculate the minimum reads required per write.

What makes this useful

The result includes cache-write premiums and invalidation risk instead of assuming every repeated token is a hit.

Frequently asked questions

When is prompt caching worth it?

Caching is most valuable when a large, byte-stable prefix is reused several times before expiration or invalidation.

What causes a prompt-cache miss?

Changes near the beginning of the cached prefix, TTL expiration, provider routing, or unsupported request shapes can force a new cache write.

Do all models charge the same cache rates?

No. Read discounts, write premiums, minimum prefix sizes, and expiration rules vary by provider and model.

Continue your analysis

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Price Change Calculator

Translate a model-price change into the exact action your SaaS business must take.

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Prompt Caching Break-Even Calculator uses current model prices and your operating assumptions to estimate business impact. Treat the output as a planning model, then replace defaults with p50, p95, and p99 telemetry from your own product.