How does OpenAI Prompt Caching work on GPT-4o?

OpenAI automatically caches input prompts longer than 1,024 tokens. When a prompt matches an existing cache entry, input tokens receive an automatic 50% discount ($1.25 per 1M tokens instead of $2.50 on GPT-4o), with zero developer configuration required.

How does Anthropic Claude Prompt Caching compare to OpenAI?

Anthropic Claude 3.5 requires explicit cache control breakpoints in your API request, but offers a massive 90% discount on cache hits ($0.30 per 1M tokens on Sonnet). Writing to cache costs 25% extra initially, but pays for itself after just 2 queries.

When does Prompt Caching save the most money?

Prompt Caching yields the highest ROI in multi-turn conversational agents, RAG workflows with large static reference documents, codebase analysis, and apps with extensive system instructions.

LLM Prompt Caching Cost Optimizer 2026

Model real-world financial savings with Prompt Caching on Claude 3.5, OpenAI GPT-4o, and DeepSeek. Calculate exact cache hit ratios, write overheads, and annual net runway preservation.

💡 Related Calculators: ChatGPT API Cost Calculator • Tokens to Words Converter • RAG Cost Calculator

2026 Prompt Caching Discounts by Provider

Empirical caching discounts, minimum token thresholds, and Time-to-Live (TTL) retention policies.

Provider / Model	Standard Input	Cached Read Rate	Effective Discount	Min Cache Threshold	Cache TTL Window
DeepSeek (V3 & R1)	$0.14 – $0.55	$0.014 – $0.14	-75% to -90%	Automatic (Prefix)	Server-side dynamic
Anthropic Claude 3.5	$3.00 (Sonnet)	$0.30	-90%	1,024 Tokens	5 Minutes (Rolling)
OpenAI (GPT-4o / o1)	$2.50 (4o)	$1.25	-50%	1,024 Tokens	5–10 Minutes
Google Gemini 1.5 Pro	$1.25 / 1M	$0.31	-75%	32,768 Tokens	Explicit Storage Fee

Frequently Asked Questions

What causes a prompt cache miss in production systems?

Prompt caching operates on exact prefix matching. Altering a single character, injecting dynamic timestamps at the start of your prompt, or shuffling few-shot examples invalidates the entire cache chain from that point forward, triggering full standard billing.

Is there a cache write cost before saving money on reads?

Anthropic charges a 25% premium for initial cache creation ($3.75/M for Claude 3.5 Sonnet). If the cached prompt is reused at least 2 times within its 5-minute rolling TTL window, net cost turns immediately positive. OpenAI and DeepSeek do not charge extra for cache writes.

How does prompt caching improve latency alongside cost savings?

Because the GPU skips recomputing attention matrices for the cached tokens, Time-to-First-Token (TTFT) latency drops by 50% to 80% on long 20k+ token prompts, delivering an instantly responsive user experience.