GPT-4 Turbo vs GPT-5.5 (2026-04-24 · US)
GPT-4 Turbo (Azure OpenAI, 128,000-token context) versus GPT-5.5 (2026-04-24 · US) (Azure OpenAI, 922,000-token context). GPT-5.5 (2026-04-24 · US) is cheaper by 13% on a blended token mix. GPT-5.5 (2026-04-24 · US) uniquely supports vision input and pdf input. Use the live calculator below to plug your real usage shape into both, then route the winner via Agent Command Center for shadow A/B without code changes.
Bottom line — GPT-4 Turbo vs GPT-5.5 (2026-04-24 · US)
GPT-4 Turbo and GPT-5.5 (2026-04-24 · US) target overlapping workloads but differ sharply on economics. GPT-5.5 (2026-04-24 · US) runs roughly 13% cheaper on a blended input-plus-output token mix, which translates to approximately $16,500 per month at mid-market volume (100K requests/day). The gap compounds at enterprise scale, making the cost axis the first filter most teams apply when deciding between these two models.
GPT-5.5 (2026-04-24 · US) ships a 922,000-token context window, 7.2x larger than GPT-4 Turbo's 128,000 tokens. That headroom matters for long-document RAG pipelines, multi-turn agent sessions that accumulate tool-call history, and codebases where the entire repository needs to fit in a single prompt. If your average prompt stays under 128,000 tokens, the extra context on GPT-5.5 (2026-04-24 · US) is insurance you may never use — and GPT-4 Turbo may win on other axes.
On capability surface area, the models diverge: GPT-5.5 (2026-04-24 · US) supports vision input where the other does not; GPT-5.5 (2026-04-24 · US) supports pdf input where the other does not; GPT-5.5 (2026-04-24 · US) supports structured output (json schema) where the other does not. These differences are binary — either your workload needs the capability or it does not. Check whether any critical path in your agent pipeline depends on a capability only one model provides before committing to a migration.
For teams evaluating both models, the recommended path is a shadow A/B test: route production traffic through an OpenAI-compatible gateway, mirror a percentage to the candidate model, score both responses with an automated evaluator (faithfulness, tool-call correctness, latency), and compare cohort-level metrics over two weeks. Future AGI Agent Command Center supports this pattern with a single `base_url` change and built-in evaluators from the ai-evaluation SDK.
Live workload comparison
Same workload run through both models. The cheaper one is highlighted.
strategy: cost-optimized
primary:
model: us-gpt-5-5-2026-04-24
provider: azure-openai
fallback:
model: gpt-4-turbo
provider: azure-openai
shadow: { sample_rate: 0.05 } # mirror 5% of traffic to compare quality live| GPT-4 Turbo | GPT-5.5 (2026-04-24 · US) | |
|---|---|---|
| Input price | $11.00/M | $5.50/M |
| Output price | $33.00/M | $33.00/M |
| Context window | 128,000 | 922,000 |
| Max output | 4,096 | 128,000 |
| Function calling | ✓ | ✓ |
| Vision | — | ✓ |
| Audio input | — | — |
| Reasoning | — | ✓ |
| Prompt caching | — | ✓ |
| Structured output | — | ✓ |
| Pricing verified | Oct 22, 2026 | Oct 22, 2026 |
Benchmark comparison
Side-by-side public benchmark scores. Greener bar = winner.
Cost at scale: monthly spend at three usage volumes
Estimated monthly cost assuming 1,000 input + 200 output tokens per request — a realistic chat-agent shape. Adjust your own usage in the calculator at the top of this page for an exact number.
| Scale | GPT-4 Turbo | GPT-5.5 (2026-04-24 · US) | Delta |
|---|---|---|---|
| Startup 10K requests/day | $5,280 /mo | $3,630 /mo | $1,650/mo |
| Mid-market 100K requests/day | $52,800 /mo | $36,300 /mo | $16,500/mo |
| Enterprise 1M requests/day | $528,000 /mo | $363,000 /mo | $165,000/mo |
At enterprise scale (1M requests/day), a difference of even ~10% in unit price compounds into thousands of dollars per month. Cached input pricing and batch tiers can shift this further — both are surfaced on each model's own page.
When to choose which
Picked from the data above — not vendor marketing. Match the rules to your workload, not the other way around.
Your workload needs long context — GPT-5.5 (2026-04-24 · US) fits 922,000 tokens versus the other model's 128,000, enough headroom for full books, large codebases, or 100+ page documents in one shot.
Your inputs include screenshots, diagrams, or product photos — GPT-5.5 (2026-04-24 · US) accepts image input natively, the other doesn't.
Your tasks involve multi-step planning or math-heavy reasoning — GPT-5.5 (2026-04-24 · US) ships a native reasoning mode that explicitly thinks before responding, the other doesn't.
You re-send the same large system prompt across requests — GPT-5.5 (2026-04-24 · US) supports prompt caching, cutting input cost on repeat hits.
Capability diff — what you gain and lose on the swap
A specific list of what each model has that the other doesn't. If your workload depends on a row in Only GPT-4 Turbo, switching to GPT-5.5 (2026-04-24 · US) means re-architecting that path (and vice versa).
- • Vision input
- • PDF input
- • Structured output (JSON schema)
- • Prompt caching
- • Native reasoning mode
Capabilities both share (3)
- ✓ Function calling
- ✓ Parallel tool calls
- ✓ Streaming
Migration considerations
Concrete differences to wire through your stack before you flip traffic from one to the other.
- Context window changes up 620% when moving from GPT-4 Turbo (128,000) to GPT-5.5 (2026-04-24 · US) (922,000). Re-check any prompt that relies on cramming long history or documents.
- Max output tokens differ: 4,096 on GPT-4 Turbo vs 128,000 on GPT-5.5 (2026-04-24 · US). Long-form generation tasks may truncate differently — adjust streaming UI and chunking accordingly.
- GPT-5.5 (2026-04-24 · US) has capabilities GPT-4 Turbo lacks: Vision input, PDF input, Structured output (JSON schema), Prompt caching, Native reasoning mode. Worth wiring through the agent design before commit.
How to A/B test GPT-4 Turbo vs GPT-5.5 (2026-04-24 · US) in production
If you're stuck between the two, run them side-by-side on real traffic. Four steps the Future AGI team uses internally:
- 1. Point your existing OpenAI SDK at
https://gateway.futureagi.com/v1. No code change beyondbase_urland a virtual key. - 2. Mark GPT-4 Turbo primary, mirror 20% of traffic to GPT-5.5 (2026-04-24 · US) in shadow mode. Both responses are logged; only the primary is served to users.
- 3. Score every shadow response with an evaluator — faithfulness, tool-call correctness, response latency, cost. Built-in evaluators in ai-evaluation cover the common axes.
- 4. Compare cohort-level metrics after two weeks. Switch primary when the candidate wins on what matters to your workload — and stays within your latency budget.
Full walkthrough on the Agent Command Center page.
FAQ — GPT-4 Turbo vs GPT-5.5 (2026-04-24 · US)
Which is cheaper, GPT-4 Turbo or GPT-5.5 (2026-04-24 · US)? ▾
GPT-5.5 (2026-04-24 · US) is cheaper by roughly 13% on a blended input + output token mix. Input prices are $11.00/M for GPT-4 Turbo versus $5.50/M for GPT-5.5 (2026-04-24 · US); output prices are $33.00/M versus $33.00/M. The exact savings depend on your input:output ratio — use the live calculator above to plug in your own request shape.
What is the context window of GPT-4 Turbo versus GPT-5.5 (2026-04-24 · US)? ▾
GPT-4 Turbo supports up to 128,000 tokens of context. GPT-5.5 (2026-04-24 · US) supports up to 922,000 tokens. GPT-5.5 (2026-04-24 · US) has the larger window by a factor of 7.2x, which matters for long-document RAG, multi-turn agent sessions, and tasks that need to keep an entire codebase in working memory.
Do GPT-4 Turbo and GPT-5.5 (2026-04-24 · US) both support tool calling? ▾
Yes — both GPT-4 Turbo and GPT-5.5 (2026-04-24 · US) support native function calling. Both also support structured output via JSON schema, so an agent can be ported between them with the same tool definitions.
Can GPT-4 Turbo and GPT-5.5 (2026-04-24 · US) process images? ▾
GPT-5.5 (2026-04-24 · US) accepts native image input. GPT-4 Turbo does not — you would need to route image-heavy workloads through GPT-5.5 (2026-04-24 · US) or add a separate vision model in front of GPT-4 Turbo.
Which model supports prompt caching for cost reduction? ▾
GPT-5.5 (2026-04-24 · US) supports prompt caching; the other does not. If your agent has a stable system prompt + retrieval context block that repeats across requests, GPT-5.5 (2026-04-24 · US) gives you a 50–90% discount on those repeated input tokens at the provider level.
When should I choose GPT-4 Turbo over GPT-5.5 (2026-04-24 · US)? ▾
On the data this page surfaces, GPT-4 Turbo is the right pick when GPT-5.5 (2026-04-24 · US)'s lower price or different capability profile aren't a fit for your workload. Run the live calculator above against your actual usage shape to confirm.
When should I choose GPT-5.5 (2026-04-24 · US) over GPT-4 Turbo? ▾
Your workload needs long context — GPT-5.5 (2026-04-24 · US) fits 922,000 tokens versus the other model's 128,000, enough headroom for full books, large codebases, or 100+ page documents in one shot. Your inputs include screenshots, diagrams, or product photos — GPT-5.5 (2026-04-24 · US) accepts image input natively, the other doesn't. Your tasks involve multi-step planning or math-heavy reasoning — GPT-5.5 (2026-04-24 · US) ships a native reasoning mode that explicitly thinks before responding, the other doesn't. You re-send the same large system prompt across requests — GPT-5.5 (2026-04-24 · US) supports prompt caching, cutting input cost on repeat hits.
How do I A/B test GPT-4 Turbo against GPT-5.5 (2026-04-24 · US) in production? ▾
Route both through an OpenAI-compatible gateway like Future AGI Agent Command Center with shadow mode enabled. Send 100% of traffic to your primary model, mirror 10–20% to the candidate, score every response with an evaluator (faithfulness, tool-call correctness, response time), and compare cohort-level metrics for two weeks. Switch when the candidate wins on the metrics that matter to your workload and stays within your latency budget.