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Fit {{ resultsReady ? fitLabel : '—' }} Required {{ resultsReady ? formatDwpd(computation.values.required_vendor_dwpd) : '—' }} Allowance {{ resultsReady ? formatDailyWrites(computation.values.allowed_daily_writes_gb) : '—' }}
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Choose DWPD or TBW exactly as the data sheet states it.
Decimal terabytes, matching normal SSD data-sheet capacity.
TB
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Use the warranty term tied to the entered endurance rating.
years
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Use the average host write size, not the NAND page size.
KiB
A 24-hour window means the entered rate is sustained all day.
h/day
The neutral value is 1 copy.
Use 1 when the entered workload already describes one drive.
Match the warranty term unless the deployment has a different retirement target.
years
Applied before workload fit and required-spec sizing.
%
This is a user-authored planning assumption, not a vendor guarantee adjustment.
%
Used for wear-runway alerts; it does not change the endurance budget.
%
A value of 1 means NAND writes match host writes.
×
The default 25% step is used only for the scenario artifact.
%
Vendor capacity and TBW normally use decimal units.
Leave at 0 when no cumulative write counter is available.
Both service age and cumulative writes are needed for an observed pace.
days
Leave at 0 when the controller does not expose this estimate.
%
This changes the planning trigger, not the endurance estimate.
days
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Calculation method:
Vendor host-write rating, planning factors, and per-drive workload stay separate.
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ScenarioWrites/dayRequired DWPDCoverageCopy
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The chart renderer is unavailable. The same endurance values remain available in the metrics and scenario artifacts.

SignalValueInterpretationCopy
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Solid-state drive endurance describes a write budget, not a scheduled failure date. Vendors usually express that budget as terabytes written (TBW) over the warranty or as drive writes per day (DWPD), the number of complete user-capacity writes allowed each day across the stated warranty period. Capacity and warranty must accompany a DWPD figure before it can be compared with TBW.

Both ratings normally refer to host writes measured under a defined qualification workload. Real wear also depends on write size, randomness, unused capacity, overprovisioning, garbage collection, firmware, temperature, and write amplification inside the drive. A workload that stays below the nominal host-write budget can still deserve replacement for media errors, falling spare capacity, latency, or other health signals.

TBW
The rated cumulative host-write amount associated with the drive and warranty.
DWPD
Rated full-capacity host writes per day over the warranty period.
Write amplification
The ratio of NAND writes to host writes; useful for estimating internal media traffic but not for rewriting a vendor host-write rating.
Percentage Used
An NVMe controller estimate of consumed subsystem life. It is vendor-derived and may continue above 100.

Workload topology matters before any endurance comparison. A replicated application can create more than one device write for each source write, while striping can divide the stream across several drives. Sustained MB/s and write IOPS also need an active daily window; treating a peak rate as continuous for 24 hours can overstate required endurance by a large factor.

Planning reserve and derating are explicit caution factors, not changes to the warranty. Reserve holds back part of the rated budget for uncertainty. Derating applies another reduction for a harsher or less certain environment. Monitoring then adds observed write counters and service age to estimate pace, but no single endurance number replaces backups, redundancy, error monitoring, and a tested replacement process.

How to Use This Tool:

Start with the exact rating basis in the drive data sheet, then translate the host workload into a per-drive daily amount.

  1. Choose DWPD rating or TBW rating exactly as published. Enter the associated user Drive capacity and Warranty period.
  2. Select a Workload input. Daily GB needs no time conversion; sustained MB/s and write IOPS need the active write window, and IOPS also needs the average host write block size.
  3. Set Write copies per host write and Drives sharing workload to describe the device-level stream. Use 1 and 1 when the input already represents one drive.
  4. Enter the Target service life. Add Endurance reserve or Endurance derating only as documented planning assumptions, and keep the decimal or binary unit base consistent with the workload source.
  5. Read Spec Gap for the required vendor TBW and DWPD. Use Write Scenarios to see how workload growth changes coverage and Warranty Runway to compare cumulative planned writes with the effective budget.
  6. For an installed drive, enter the cumulative SMART write counter in its native unit and the Service age. Add SMART Percentage Used only as a controller cross-check, then review Wear Audit alongside media errors and spare-capacity warnings.

Interpreting Results:

Vendor coverage compares the published rating with the vendor rating required after reserve and derating. Coverage below 100% is Below requirement. Coverage from 100% up to but not including 125% is a Slim margin. Coverage at or above 125% is Comfortable. These are planning labels, not vendor warranty categories.

Projected life assumes the entered daily host-write pace remains constant. Warning runway stops at the selected percentage of the effective budget rather than full exhaustion. A zero workload reports an open sizing state instead of inventing an infinite life.

Observed-write forecasts require both a positive cumulative counter and positive service age. Compare Days to warning, Days to exhaustion, and Replacement action with error logs, redundancy, procurement lead time, and maintenance windows. A controller-implied TBW derived from Percentage Used is a cross-check; disagreement can reflect vendor estimation, unit interpretation, or a workload that changed over time.

Technical Details:

The endurance budget is normalized in decimal terabytes for vendor-rating arithmetic. Workload entries may use a decimal base of 1,000 or a binary base of 1,024 for rate conversions and daily-write units. Keeping the base consistent matters because it changes the amount represented by the same digits.

Formula Core

A DWPD rating becomes TBW by multiplying user capacity by complete writes per day and the number of warranty days. A TBW entry is used directly.

Trated=C×D×365×Y

The reverse conversion divides rated TBW by the same capacity and warranty term. Reserve and derating then reduce the budget multiplicatively.

Teffective=Trated ×(1−r100) ×(1−d100)

Workload Transformation Core

Input pathSource daily writes
Average volumeEntered GB/day
Sustained rateMB/s × 3,600 × active hours ÷ selected unit base
Write IOPSIOPS × block size in KiB × 1,024 × 3,600 × active hours ÷ unit base³

The source stream is multiplied by write copies and divided evenly across the entered drive count.

Wdrive=Wsource×kn

Actual DWPD divides per-drive daily TB by user capacity. The vendor rating required for the target life reverses the reserve and derating factors, so a stricter planning factor raises required vendor TBW and DWPD.

Trequired vendor=Wdrive TB per day×365×Ytarget(1−r100)(1−d100)

Vendor coverage is rated TBW divided by required vendor TBW, multiplied by 100. Projected life divides effective TBW by annual per-drive writes. Warning runway uses only the selected 50% through 99% share of the effective budget. Estimated NAND writes equal per-drive host writes times the entered write-amplification factor, but this does not reduce the vendor host-write budget a second time.

Wear Forecast Core

Observed counters are converted to decimal TB. For NVMe Data Units Written, one counter unit represents 1,000 blocks of 512 bytes, or 512,000 bytes. Observed daily pace divides converted writes by service days. Remaining effective TBW and the distance to the warning point are then divided by that pace to estimate days.

StatusExact boundary
Below requirementVendor coverage < 100%
Slim margin100% ≤ vendor coverage < 125%
ComfortableVendor coverage ≥ 125%
No loadPer-drive host writes = 0 GB/day

The controller-implied budget divides observed writes by Percentage Used as a decimal fraction. That cross-check is active only when both figures are positive. The model accepts Percentage Used from 0% through 255%, reflecting the field's ability to continue beyond nominal life consumption.

Accuracy Notes:

Endurance planning is sensitive to rating scope, workload measurement, and changing operating conditions.

  • Use the user capacity, warranty term, TBW or DWPD, and workload basis from the same vendor data sheet.
  • Confirm whether the workload value is a source stream, an array total, or one drive's writes before applying copies and drive count.
  • Do not multiply vendor TBW by write amplification. The rating and workload comparison use host writes; the amplification estimate is shown separately as NAND traffic.
  • SMART attributes outside the standardized NVMe fields can be vendor-specific. Verify counter units before entering raw values.
  • A projected write runway does not account for sudden controller failure, media errors, power-loss damage, firmware defects, or retention limits. Keep tested backups and monitor the complete health report.

Worked Examples:

TBW-rated drive with observed wear

A 1 TB drive rated for 600 TBW over five years receives 270 GB/day. Holding back an 8% reserve leaves 552 TB effective, and the five-year target needs about 535.60 TB of vendor rating. Coverage is about 112.02%, so the result is a slim margin. If the drive has written 200 TB in 1,000 days, the observed pace is 200 GB/day. The remaining effective budget is 352 TB, giving about 1,760 days to exhaustion at that pace; a 60-day replacement lead moves the action point to about 1,700 days. A controller report of 40% used implies about 500 TB total, which is a useful cross-check rather than a replacement for the vendor rating.

References: