Cost formula
Chat cost = sum over turns of (input tokens including history / 1M × input price) + (output tokens / 1M × output price); Completion cost = (prompt tokens / 1M × input price) + (output tokens / 1M × output price)
Calculator
Chat vs Completion cost comparer
See how growing chat history changes your bill compared with stateless completion-style requests on the same model.
Chat vs completion
Completion is lower
$0.0055731.3% gap
Completion wins when chat history balloons — each turn re-bills prior context as input.
Chat$0.0178
Completion$0.0122
Chat tokens4,948
Completion tokens2,720
Turns4
Completion reqs4
Workloads
Chat & completion inputs
Chat re-sends growing history; completion stays stateless.
Token shape
Where tokens go
Completion wins when chat history balloons — each turn re-bills prior context as input.
Completion wins when chat history balloons — each turn re-bills prior context as input.
Chat cost grows with history because prior turns are usually re-sent as input. Rates updated 2026-07-31. Approximate static list prices for planning only. Always verify against each provider’s official pricing page before production budgeting.
Guide
How to get value from this calculator
Compare chat-style API usage against legacy completion-style calls for the same workload. Chat endpoints carry message overhead and often repeat system context each turn, which can inflate input tokens at monthly volume. Use this to decide which API shape fits your product and budget.
Why it matters
Chat APIs simplify product logic but can multiply input tokens when conversation history grows. Teams that assume chat and completion cost the same often miss the compounding effect of multi-turn context on monthly bills.
How to use it
- Define your typical conversation length in turns and average tokens per turn.
- Enter system prompt size and whether it is resent every turn.
- Model the same task as a single-shot completion with equivalent total tokens.
- Compare total input, output, and combined monthly cost for both patterns.
- Compare chat vs completion on the token-shape bars and read when each wins.
- Note whether prompt caching applies to repeated system or tool context.
- Verify pricing parity on your provider—some models price chat and completion identically per token.
Planning tips
- Truncate or summarize history after N turns to cap input growth in production chat.
- Prompt caching dramatically reduces repeated system prompt cost in chat—model a realistic hit rate.
- Single-turn tasks (classification, extraction) may be cheaper via completion or a minimal chat call.
- Output token pricing is identical regardless of API style—focus comparisons on input-side differences.
- Watch the token-shape bars as history grows—they show when chat stops winning on cost.
- Log actual input tokens per turn in staging before locking in architecture.
Frequently asked questions
Is chat always more expensive than completion?
Not always. Short single-turn chats with small history can match completion cost. Multi-turn threads with growing context usually cost more unless you truncate history or use caching.
Do providers charge different rates for chat vs completion?
Most providers bill the same per-token input and output rates regardless of endpoint. The cost difference comes from token volume, not a separate chat surcharge.
How should I plan for monthly volume?
Estimate active sessions per day, average turns per session, and tokens per turn. Multiply out to monthly input and output totals, then apply list prices as a planning estimate only.
Are CentsPerToken figures binding quotes?
No. All numbers are approximate planning aids based on static list prices. Confirm official pricing before production budgeting.