Pick Gemini 3.5 Flash for speed — roughly 4x faster than rivals or cost — about a third the price. Pick GPT-5.4 for strong general-purpose default or coding and software engineering. On a tight budget at scale, Gemini 3.5 Flash is the value pick.
Gemini 3.5 Flash (Google) and GPT-5.4 (OpenAI) are two of the models people most often weigh against each other in 2026. Gemini 3.5 Flash is google's fast, cheap class that now beats last year's premium Pro — the value-and-reach play. GPT-5.4 is openAI's 2026 workhorse — unifies Codex and GPT into a strong default that costs half of GPT-5.5. Their biggest split is price, and the breakdown below shows exactly how that plays out for your workload.
Key differences
Price: Gemini 3.5 Flash is about 1.7× cheaper on input ($1.5/$9 per 1M tokens vs $2.5/$15 per 1M tokens) — modest, but it adds up at steady volume.
Context window: both advertise 1M (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
Recency: Gemini 3.5 Flash is the newer model by about 3 months (released May 19, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Gemini 3.5 Flash
GPT-5.4
Provider
Google (US)
OpenAI (US)
Released
May 19, 2026
March 5, 2026
Context window
1M (~1,500 pages)
1M (~1,500 pages)
Price (in/out)
$1.5/$9 per 1M tokens
$2.5/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, audio, video, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Speed — roughly 4x faster than rivals: Gemini 3.5 Flash — A core design strength of Gemini 3.5 Flash.
Cost — about a third the price: Gemini 3.5 Flash — A core design strength of Gemini 3.5 Flash.
Default in the Gemini app and Search AI Mode: Gemini 3.5 Flash — A core design strength of Gemini 3.5 Flash.
Strong general-purpose default: GPT-5.4 — A core design strength of GPT-5.4.
Coding and software engineering: GPT-5.4 — A core design strength of GPT-5.4.
Document understanding and tool use: GPT-5.4 — A core design strength of GPT-5.4.
Lowest cost at scale: Gemini 3.5 Flash — At $1.5/$9 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume: Gemini 3.5 Flash — At $1.5/$9 per 1M tokens it undercuts GPT-5.4, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is speed — roughly 4x faster than rivals: Gemini 3.5 Flash — It is specifically built for that.
Anyone whose priority is strong general-purpose default: GPT-5.4 — That is its strongest area.
Gemini 3.5 Flash: where it fits
Google's fast, cheap class that now beats last year's premium Pro — the value-and-reach play. Released May 19, 2026 by Google, it is built for speed — roughly 4x faster than rivals, cost — about a third the price, default in the Gemini app and Search AI Mode, and high-volume multimodal work.
Its trade-offs are real: flash tier, not the deepest reasoning, and pro-tier 3.5 held back at launch. At $1.5 in / $9 out per million tokens, it sits in the mid price band.
GPT-5.4: where it fits
OpenAI's 2026 workhorse — unifies Codex and GPT into a strong default that costs half of GPT-5.5. Released March 5, 2026 by OpenAI, it is built for strong general-purpose default, coding and software engineering, document understanding and tool use, and 1M context with good token efficiency.
Its trade-offs: topped by GPT-5.5 on the hardest tasks, and pricier than open-weight rivals. At $2.5 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Gemini 3.5 Flash and GPT-5.4 overlap enough that the right pick depends on your specific job. Gemini 3.5 Flash costs less per token; and each leads in its own area — Gemini 3.5 Flash for speed — roughly 4x faster than rivals, GPT-5.4 for strong general-purpose default. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is Gemini 3.5 Flash or GPT-5.4 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Gemini 3.5 Flash leans toward speed — roughly 4x faster than rivals while GPT-5.4 leans toward strong general-purpose default, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Gemini 3.5 Flash or GPT-5.4?
Gemini 3.5 Flash is cheaper — $1.5/$9 per 1M tokens vs $2.5/$15 per 1M tokens, roughly 1.7× apart on input.
Which has the bigger context window?
Both advertise 1M (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Gemini 3.5 Flash and GPT-5.4 together?
Yes — a multi-model platform like LumiChats gives you Gemini 3.5 Flash, GPT-5.4 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Gemini 3.5 Flash or GPT-5.4?
Gemini 3.5 Flash — released May 19, 2026, about 3 months after GPT-5.4.
Gemini 3.5 Flash vs GPT-5.4
Google · US | OpenAI · US · Updated June 2026
Quick verdict
Pick Gemini 3.5 Flash for speed — roughly 4x faster than rivals or cost — about a third the price. Pick GPT-5.4 for strong general-purpose default or coding and software engineering. On a tight budget at scale, Gemini 3.5 Flash is the value pick.
Gemini 3.5 Flash (Google) and GPT-5.4 (OpenAI) are two of the models people most often weigh against each other in 2026. Gemini 3.5 Flash is google's fast, cheap class that now beats last year's premium Pro — the value-and-reach play. GPT-5.4 is openAI's 2026 workhorse — unifies Codex and GPT into a strong default that costs half of GPT-5.5. Their biggest split is price, and the breakdown below shows exactly how that plays out for your workload.
Key differences at a glance
▸Price: Gemini 3.5 Flash is about 1.7× cheaper on input ($1.5/$9 per 1M tokens vs $2.5/$15 per 1M tokens) — modest, but it adds up at steady volume.
▸Context window: both advertise 1M (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
▸Recency: Gemini 3.5 Flash is the newer model by about 3 months (released May 19, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Gemini 3.5 Flash
GPT-5.4
Provider
Google (US)
OpenAI (US)
Released
May 19, 2026
March 5, 2026
Context window
1M (~1,500 pages)
1M (~1,500 pages)
Price (in/out)
$1.5/$9 per 1M tokens
$2.5/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, audio, video, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Speed — roughly 4x faster than rivals
Gemini 3.5 Flash
A core design strength of Gemini 3.5 Flash.
Cost — about a third the price
Gemini 3.5 Flash
A core design strength of Gemini 3.5 Flash.
Default in the Gemini app and Search AI Mode
Gemini 3.5 Flash
A core design strength of Gemini 3.5 Flash.
Strong general-purpose default
GPT-5.4
A core design strength of GPT-5.4.
Coding and software engineering
GPT-5.4
A core design strength of GPT-5.4.
Document understanding and tool use
GPT-5.4
A core design strength of GPT-5.4.
Lowest cost at scale
Gemini 3.5 Flash
At $1.5/$9 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Gemini 3.5 Flash
At $1.5/$9 per 1M tokens it undercuts GPT-5.4, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is speed — roughly 4x faster than rivals
→ Gemini 3.5 Flash
It is specifically built for that.
Anyone whose priority is strong general-purpose default
→ GPT-5.4
That is its strongest area.
Gemini 3.5 Flash: where it fits
Google's fast, cheap class that now beats last year's premium Pro — the value-and-reach play. Released May 19, 2026 by Google, it is built for speed — roughly 4x faster than rivals, cost — about a third the price, default in the Gemini app and Search AI Mode, and high-volume multimodal work.
Its trade-offs are real: flash tier, not the deepest reasoning, and pro-tier 3.5 held back at launch. At $1.5 in / $9 out per million tokens, it sits in the mid price band.
GPT-5.4: where it fits
OpenAI's 2026 workhorse — unifies Codex and GPT into a strong default that costs half of GPT-5.5. Released March 5, 2026 by OpenAI, it is built for strong general-purpose default, coding and software engineering, document understanding and tool use, and 1M context with good token efficiency.
Its trade-offs: topped by GPT-5.5 on the hardest tasks, and pricier than open-weight rivals. At $2.5 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Gemini 3.5 Flash and GPT-5.4 overlap enough that the right pick depends on your specific job. Gemini 3.5 Flash costs less per token; and each leads in its own area — Gemini 3.5 Flash for speed — roughly 4x faster than rivals, GPT-5.4 for strong general-purpose default. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Gemini 3.5 Flash and GPT-5.4 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Gemini 3.5 Flash leans toward speed — roughly 4x faster than rivals while GPT-5.4 leans toward strong general-purpose default, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Gemini 3.5 Flash or GPT-5.4?
Gemini 3.5 Flash is cheaper — $1.5/$9 per 1M tokens vs $2.5/$15 per 1M tokens, roughly 1.7× apart on input.
Which has the bigger context window?
Both advertise 1M (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Gemini 3.5 Flash and GPT-5.4 together?
Yes — a multi-model platform like LumiChats gives you Gemini 3.5 Flash, GPT-5.4 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Gemini 3.5 Flash or GPT-5.4?
Gemini 3.5 Flash — released May 19, 2026, about 3 months after GPT-5.4.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.