Calwarden

GPT API Cost Calculator

Estimate daily and monthly GPT-style API costs from your own prompt and completion token prices.

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Inputs

tokens/call
tokens/call
calls/day
days

Your values stay on this device.

Results

Daily Cost

Estimated token cost for one day of API calls.

Monthly Cost$101.25
Cost Per Call$0.00
Monthly Input Tokens45,000,000
Monthly Output Tokens15,000,000

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Assumptions

  • Prices are entered manually and are not fetched from any provider.
  • Each call uses the same average prompt and completion token counts.
  • The estimate excludes retries, caching discounts, storage, fine-tuning, taxes, and non-token fees.

Sensitivity preview

Prompt Tokens -10%: Daily Cost $3.26

Prompt Tokens Current: Daily Cost $3.38

Prompt Tokens +10%: Daily Cost $3.49

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About this GPT API Cost Calculator

GPT API bills depend on how many prompt and completion tokens each call uses, multiplied by the prices on your account. This calculator keeps prices editable so estimates stay tied to your actual model choice.

When to use it

  • Forecast the monthly budget for a GPT-powered app.
  • Compare short answers versus longer completions.
  • Translate usage logs into expected invoice amounts.
  • Estimate cost changes from higher or lower daily traffic.

How to use this calculator

  1. Enter average prompt tokens and completion tokens per API call.
  2. Enter your prompt and completion prices per million tokens.
  3. Add the expected calls per day and billable days per month.
  4. Use daily cost for operations planning and monthly cost for budget reviews.

Key assumptions

  • Prices are entered manually and are not fetched from any provider.
  • Each call uses the same average prompt and completion token counts.
  • The estimate excludes retries, caching discounts, storage, fine-tuning, taxes, and non-token fees.
  • Calculations are deterministic and run locally.

Dataset sources

OpenAI API pricing
Effective date
2026-05-05
Last reviewed
2026-05-05

Use the current provider pricing page or contract terms before making purchasing decisions.

Public provider pricing page; rates can change without notice.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

Cost per call equals prompt token cost plus completion token cost. Daily cost multiplies cost per call by calls per day. Monthly cost multiplies daily cost by days per month, while monthly token totals show expected billable volume.

Inputs explained

Prompt Tokens

Tokens sent to the model in each API call, including instructions, context, user text, and tool messages.

Completion Tokens

Tokens generated by the model in each API response.

Prompt Price Per Million

Your user-entered price for one million prompt tokens.

Completion Price Per Million

Your user-entered price for one million generated tokens.

Calls Per Day

Expected API call volume in a typical day.

Days Per Month

Number of active billing days to include in the monthly estimate.

Understanding your results

Daily cost is the primary operating estimate. Monthly cost shows the likely billing-period impact, while token totals help compare against usage dashboards and quotas.

Example scenarios

Internal Assistant

An internal tool with 2,000 calls per day can be budgeted by entering average prompt and completion tokens from logs.

Launch Forecast

Before launch, estimate a conservative calls-per-day figure and adjust after real usage data arrives.

Key Features

  • Instant Calculation
  • Private & Secure
  • Mobile Optimized

Tips & Best Practices

  • Use production token logs when possible instead of rough guesses.
  • Separate prompt and completion costs to see whether context or answer length drives spend.
  • Revisit prices when changing models, regions, vendors, or negotiated plans.
  • Keep private prompts out of the calculator; only aggregate token counts are needed.

Frequently Asked Questions

Why are prices entered manually?
Provider prices change and can vary by model, region, tier, or contract. Manual prices make the estimate match the numbers you actually pay.
What is the difference between prompt and completion tokens?
Prompt tokens are sent into the model. Completion tokens are generated by the model and returned in the response.
Does this include free tiers or discounts?
No. Enter an effective price after discounts if you want the estimate to reflect a negotiated or blended rate.