Azure OpenAI PTU Calculator

📦 PTU Sizing

Normalized TPM (workload demand)

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Min PTUs Required

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Recommended PTUs (+headroom)

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Monthly capacity vs demand (per your PTU purchase, 24/7 sustained)

PTU Monthly Capacity (normalized)

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Workload Demand (uncached + 6×output)

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Capacity Used

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💡 Capacity for Your Purchase

PTUs Purchased

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Peak Input TPM

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N × TPM/PTU

Utilization @ Target

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Burst Headroom

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💰 Monthly Cost Comparison @ Target TPM

🔝 THE COMPARISON THAT MATTERS — these are the two numbers to compare. Not PTU base alone.

🎯 If you buy PTU — Effective Total/mo

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💳 If you stay on PayGo — Total/mo

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📈 PTU saves you

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PayGo − PTU Effective

PTU Effective Total breakdown — PTU base is fixed; cached input + spillover are pass-through PayGo charges that PTU cannot eliminate.

PTU Base (fixed monthly)

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+ Cached (FREE under PTU)

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+ Spillover PayGo (over capacity)

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🛍️ Buy PTU to skip spillover

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Bucket	In-capacity tokens/mo	Spillover tokens/mo	PayGo price ($/M)	Spillover $/mo
Total Spillover PayGo	—

🎯 Break-even Thresholds (when does PTU win?)

With your current PTU purchase, the table below shows the threshold for each variable (holding the others constant) where PTU + Spillover = Pure PayGo. Cross the threshold in the right direction → PTU starts saving money.

Variable	Current	Break-even threshold	To make PTU win	Note

🧮 Monthly Token Budget & PayGo Cost Breakdown

Assumes target Input TPM is sustained 24/7 for 30 days (= 43,200 min/mo).
Formula: tokens/mo = TPM × 43,200 · PayGo $/mo = (tokens/mo / 1,000,000) × price/M

Input (uncached) tokens/mo

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Input (cached) tokens/mo

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Output tokens/mo

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Bucket	TPM	Tokens / month	Price ($/M)	PayGo $/mo
Total PayGo	—	—	—	—

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📊 Cost Sensitivity Across TPM Levels

If you ran at this Input TPM continuously, how does PTU + Spillover compare with pure PayGo?

Input TPM	Util %	PTU base	Spillover PayGo	Effective Total	Pure PayGo	Savings/mo

📈 Cumulative Cost Over Time @ Target TPM