Prompt Caching

Understanding prompt caching pricing and mechanics across LLM providers

Prompt caching allows you to cache frequently-used context (system prompts, examples, documents) and reuse it across multiple requests at a discounted rate. This guide explains how caching works and is priced across different providers.

Overview

When you cache content:

1. Cache Write: You pay to store content in the cache (first use)
2. Cache Read: You pay a discounted rate when reusing cached content
3. Storage (Google only): Additional hourly storage costs

Anthropic (Claude)

Anthropic uses a simple multiplier-based pricing model for prompt caching.

Pricing Structure

Operation	Multiplier	Example (Claude Sonnet @ $3/MTok)
Cache Read	0.1×	$0.30/MTok
Cache Write (5 min)	1.25×	$3.75/MTok
Cache Write (1 hour)	2.0×	$6.00/MTok

Key Points

• TTL Options: 5 minutes or 1 hour
• Providers: Available on Anthropic API, Vertex AI, and AWS Bedrock
• Limitation: Vertex AI and Bedrock only support 5-minute caching
• Minimum: 1024 tokens for most models

Calculation Example

Base input price: $3/MTok
5-min cache write: $3 × 1.25 = $3.75/MTok
1-hour cache write: $3 × 2.0 = $6.00/MTok
Cache read: $3 × 0.1 = $0.30/MTok

Google Gemini

Google uses a multiplier plus storage cost model for context caching.

Pricing Structure

Operation	Multiplier	Storage Cost
Cache Read	0.25×	N/A
Cache Write	1.0×	+ Storage fee

Storage Rates:

• Gemini 2.5 Pro: $4.50/MTok/hour
• Gemini 2.5 Flash: $1.00/MTok/hour
• Gemini 2.5 Flash-Lite: $1.00/MTok/hour

Key Points

• TTL: 5 minutes only
• Cache Types: Implicit (automatic) and Explicit (manual)
• Minimum: 1024 tokens (Flash), 2048 tokens (Pro)
• Discount: 75% off input costs for cache reads

Calculation Example

For Gemini 2.5 Pro (≤200K tokens):

Base input price: $1.25/MTok
Storage rate: $4.50/MTok/hour

Cache write (5 min):
- Input cost: $1.25 × 1.0 = $1.25
- Storage cost: $4.50 × (5/60) = $0.375
- Total: $1.625/MTok

Cache read: $1.25 × 0.25 = $0.31/MTok

Tiered Pricing

Gemini 2.5 Pro has different rates for larger contexts:

Context Size	Input Price	Cache Read	Cache Write (5 min)
≤200K tokens	$1.25/MTok	$0.31/MTok	$1.625/MTok
>200K tokens	$2.50/MTok	$0.625/MTok	$2.875/MTok