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SQL Server Log File Growth Calculator

Estimate SQL Server transaction log generation, retained log storage, and log backup size from workload assumptions.

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Inputs

GB/day
%
days

Your values stay on this device.

Results

Retained Log Storage
Daily Log Generation165
Average Log Backup Size3.44
Log Backups per Day24

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Assumptions

  • Daily log generation is averaged.
  • Compression ratio applies to retained log backups.
  • Database names and operational details are not stored.

Sensitivity preview

Base Log Generated -10%: Retained Log Storage 519.75 GB

Base Log Generated Current: Retained Log Storage 577.5 GB

Base Log Generated +10%: Retained Log Storage 635.25 GB

Formula: Daily log GB = base GB/day * (1 + maintenance percent / 100) * (1 + bulk percent / 100). Retained GB = daily log GB * retention days / compression ratio.

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About this SQL Server Log File Growth Calculator

Transaction logs can grow rapidly when workloads, index maintenance, bulk loads, or backup schedules change. This calculator converts those assumptions into daily and retained storage estimates.

Who this calculator is for

  • Database administrators planning log storage.
  • Infrastructure teams sizing backup repositories.
  • Operations teams investigating log growth risk.

When to use it

  • Estimate daily log generation.
  • Plan retained log backup storage.
  • Compare backup intervals and compression ratios.

How to use this calculator

  1. Enter average daily transaction log volume.
  2. Add maintenance and bulk-load overhead.
  3. Set retention days, backup interval, and compression ratio.
  4. Review retained log storage and backup size.

Key assumptions

  • Daily log generation is averaged.
  • Compression ratio applies to retained log backups.
  • Database names and operational details are not stored.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

Daily log GB = base transaction GB x maintenance overhead factor x bulk overhead factor. Retained storage = daily log GB x retention days / compression ratio.
Daily log GB = base GB/day * (1 + maintenance percent / 100) * (1 + bulk percent / 100). Retained GB = daily log GB * retention days / compression ratio.

Inputs explained

Transaction log volume

Average uncompressed log generated by normal transactions each day.

Maintenance overhead

Additional log generation from index rebuilds, ETL, or maintenance jobs.

Backup interval

How frequently log backups run, used to estimate average log backup size.

Understanding your results

Retained log storage is a backup-repository planning estimate. The log file itself also needs enough room for peak activity between backups.

Example scenarios

Busy OLTP database

120 GB/day base log volume, 25% maintenance overhead, 7-day retention, and 2:1 compression requires hundreds of GB retained.

Key Features

  • Instant Calculation
  • Private & Secure
  • Mobile Optimized

Tips & Best Practices

  • Model peak maintenance days separately.
  • Monitor VLF health and autogrowth settings in SQL Server.
  • Test restores to validate log backup chains.

Frequently Asked Questions

Is this the same as database data growth?
No. This focuses on transaction log generation and retained log backups, while data growth estimates database file capacity.
Does frequent log backup reduce total generated log?
No. It usually reduces active log exposure and backup piece size, not the total log generated by the workload.
Is any infrastructure data stored?
No. The calculation runs locally in your browser and does not upload your inputs.