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RAID 10 Calculator

Last reviewed: June 24, 2026 · Formula version: RAID10-1.0 · Formula-backed planning calculator

Estimate RAID 10 mirrored stripe capacity

Estimate RAID 10 capacity for mirrored stripe sets. RAID 10 usually sacrifices half of raw capacity but offers simple rebuild behavior and strong performance characteristics.

Server-rendered example result

Example: Input: 6 drives × 12 TB, RAID 10, no hot spare, 0% overhead. Output: raw capacity 72 TB, usable capacity 36 TB, mirror overhead 36 TB, efficiency 50%.

The interactive result cards update this example when JavaScript runs, but this default snapshot is crawlable and printable.

Quick answer

RAID 10 mirrors pairs of drives, so usable capacity is roughly half of active raw capacity. Odd active drive counts are not ideal because a mirror pair cannot be completed cleanly.

Best for: comparing realistic scenarios before acting. Not for: final professional approval, emergency decisions, or replacing product labels and local requirements.

How to use the calculator

  1. Enter the measurements, quantities, costs, or target values requested above.
  2. Adjust optional assumptions such as waste, overhead, product strength, retention days, or multipliers.
  3. Read both the main result cards and any warning notes. The warnings are part of the answer, not fine print.
  4. Use the share, copy, or print/PDF controls when you want to save the scenario.

What the results mean

The first result card is the primary decision number. Supporting cards explain capacity, cost, efficiency, safety margin, input assumptions, or the next value to check. When the page returns a range, treat it as a planning envelope rather than a guaranteed price.

Formula / methodology

RAID 10 usable capacity = floor(active drives ÷ 2) × drive size × (1 − filesystem overhead).

Assumptions and limitations

  • Inputs are assumed to be measured accurately and entered in the units shown.
  • Rounding is intentional so the result is easier to use in real decisions.
  • Vendor-specific behavior, local code, product labels, and regional pricing can override a generic calculator.
  • High-risk medical, legal, tax, and emergency calculators are intentionally not published without expert review.

Example calculation

Input: 6 drives × 12 TB, RAID 10, no hot spare, 0% overhead. Output: raw capacity 72 TB, usable capacity 36 TB, mirror overhead 36 TB, efficiency 50%.

Server-rendered example result

Example: Input: 6 drives × 12 TB, RAID 10, no hot spare, 0% overhead. Output: raw capacity 72 TB, usable capacity 36 TB, mirror overhead 36 TB, efficiency 50%.

The interactive result cards update this example when JavaScript runs, but this default snapshot is crawlable and printable.

Common mistakes

  • Using an odd number of drives and expecting all drives to pair cleanly.
  • Comparing RAID 10 only by capacity instead of rebuild behavior.
  • Forgetting that a hot spare lowers active pair count.
  • Assuming every two-drive failure is survivable; it depends which mirror pair fails.

FAQ

What formula does this page use?

RAID 10 usable capacity = floor(active drives ÷ 2) × drive size × (1 − filesystem overhead).

What changes the result the most?

The most important inputs are the size, count, rate, target, or unit assumptions shown in the calculator.

Is this a final professional answer?

No. Treat it as a planning result and verify important decisions against product documentation, labels, quotes, local code, or professional guidance.

Why does this page show warnings?

Warnings call out assumptions that can materially change the result or create safety, cost, or reliability problems.

Can I share this scenario?

Yes. The share button copies a URL with the current inputs, while the canonical page remains the base calculator URL.

Last reviewed

Last reviewed: June 24, 2026. Formula version: RAID10-1.0. Index status: indexable.