How to beginner · 3 min read

How much does OpenAI fine-tuning cost

Quick answer

OpenAI fine-tuning costs include a training fee and usage fees for the fine-tuned model. As of 2026, training a fine-tuned GPT-4o model typically costs around $2,000 per 1,000 training tokens, with usage billed at standard GPT-4o rates. Always check the official OpenAI pricing page for the latest details.

PREREQUISITES

Python 3.8+
OpenAI API key (free tier works)
pip install openai>=1.0

Setup

Install the OpenAI Python SDK and set your API key as an environment variable to start fine-tuning.

bash

pip install openai>=1.0

import os
from openai import OpenAI

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

Step by step

Fine-tuning involves uploading your training data, creating a fine-tune job, and then using the fine-tuned model. Below is a simplified example for fine-tuning a GPT-4o model.

python

import os
from openai import OpenAI

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

# Step 1: Upload training data
training_file = client.files.create(
    file=open("training_data.jsonl", "rb"),
    purpose="fine-tune"
)

# Step 2: Create fine-tune job
fine_tune_job = client.fine_tunes.create(
    training_file=training_file.id,
    model="gpt-4o"
)

print(f"Fine-tune job created with ID: {fine_tune_job.id}")

output

Fine-tune job created with ID: ft-A1b2C3d4E5f6G7h8

Common variations

You can fine-tune other models like gpt-4o-mini or use asynchronous calls. Pricing varies by model size and usage.

python

import asyncio
import os
from openai import OpenAI

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

async def fine_tune_async():
    training_file = await client.files.acreate(
        file=open("training_data.jsonl", "rb"),
        purpose="fine-tune"
    )
    fine_tune_job = await client.fine_tunes.acreate(
        training_file=training_file.id,
        model="gpt-4o-mini"
    )
    print(f"Async fine-tune job ID: {fine_tune_job.id}")

asyncio.run(fine_tune_async())

output

Async fine-tune job ID: ft-Z9y8X7w6V5u4T3s2

Troubleshooting

If you see errors about file format, ensure your training data is in JSONL format with correct prompt-completion pairs.
For quota or billing errors, verify your API key permissions and billing status on the OpenAI dashboard.

✅

Key Takeaways

OpenAI fine-tuning costs include a training fee plus usage fees for the fine-tuned model.
Training costs are roughly $2,000 per 1,000 training tokens for GPT-4o as of 2026.
Always verify pricing on the official OpenAI pricing page before starting fine-tuning.
Use the OpenAI Python SDK v1+ with environment variables for secure API key management.
Fine-tuning supports multiple models and async usage for flexible workflows.

Verified 2026-04 · gpt-4o, gpt-4o-mini

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