Free tool · Mac Care

Backup Planner

Work out how big a Time Machine drive your Mac needs, how long until old backups start to be removed, and how long a first cloud upload or a full restore will take. Then tick through a 3-2-1 checklist and a quarterly restore drill.

Runs entirely in your browser. Nothing you enter is uploaded.

Your Mac and your backups

Sizes accept 500, 500 GB, or 1.5 TB. All sizes are decimal gigabytes (1 GB is 1,000,000,000 bytes), the way drive makers count.

Apple menu > System Settings > General > Storage. Use the space that is used, not the total.

Used space today minus used space a few months ago, divided by the months. Leave blank if you do not know; enter 0 only if your data stays the same size.

The internal disk's full size, such as 512 GB or 1 TB. Disk Utility shows it too: View > Show All Devices, select the internal drive, click Info. Apple's sizing advice is based on it.

Printed on the box. Or open Disk Utility, choose View > Show All Devices, select the drive, and click Info.

Everyday work: documents, mail, a few projects. We plan with the backup using 1.5x your data. That multiplier is our assumption, not an Apple figure.

How long the drive should last before you outgrow it. A longer plan asks for a bigger drive today.

Where does your offsite copy live?

From any speed test. Mbps means megabits per second. A result in MB/s is megabytes: type it with its unit, like 2.5 MB/s.

Same speed test. Many home connections download much faster than they upload.

Overhead, shared Wi-Fi, many small files, and provider limits all take a share. 80% is a planning allowance, not a measurement.

Your plan

Enter how much data you want to back up and your plan will appear here.

Start with the size of your data. Everything else is optional, and each extra value adds one more line to the plan.

These are planning estimates in decimal GB. Real transfers and real backup sizes vary with your files and your connection.

Checklists

The 3-2-1 checklist

0 of 6 done. Three copies, on two kinds of storage, with one offsite.

Quarterly restore drill

0 of 6 done. A backup you have not restored from is a guess.

No drill recorded yet.

Your entries and checklist progress are saved in this browser only (localStorage, key lhp.backupPlanner.v1). Nothing is uploaded.

How to use it

  1. Read your used space.Choose Apple menu > System Settings > General > Storage (macOS Ventura 13 or later) and note the space used. If it is higher than you expected, our guide to what to delete when your Mac storage is full helps you trim it first.
  2. Estimate monthly growth.Compare today’s used space with a figure from a few months ago and divide by the months between. Leave it blank if you do not know; enter 0 only if your data stays the same size.
  3. Add your Mac’s total storage and your drive.Both are optional. The total adds Apple’s sizing guidance to the plan, and the drive lets the planner show how far it will stretch.
  4. Choose your offsite method. For a cloud service, run any speed test and enter the upload and download speeds. A rotated drive has nothing to transfer.
  5. Read the plan, then tick the checklists. Progress and your last drill date stay in this browser.

How it works

Drive size

Apple’s guidance is a backup disk with “at least twice the storage capacity of your Mac”, so 2 TB for a 1 TB Mac. That is tied to the Mac’s capacity, not to how much of it you use. Apple publishes no formula based on used space, so the planner adds a labelled rule of thumb of its own: twice the data you expect to hold at the end of your planning horizon.

The extra room pays for versions. Per Apple, Time Machine makes hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for all previous months.

When the drive fills

Apple says that when the disk runs low, “Time Machine deletes older backups in order to create newer ones”, and it never deletes the last remaining backup. A full drive means a shorter history, not a stopped backup.

The months figure assumes the backup is your data times a history multiplier (1.2, 1.5, or 2; our assumption) and counts how long until growing data reaches the drive divided by that multiplier. Treat it as a direction, not a date.

Transfer times

Time is gigabytes times 8,000, divided by speed in Mbps times the usable share, giving seconds. Everything is decimal: 1 GB is 1,000,000,000 bytes, which is how drive makers and speed tests count. Type GiB and the tool converts (1 GiB is about 1.074 GB). The 80% default is an allowance for overhead and shared connections, not a measurement.

The first cloud backup is a full copy sent over your upload link, often the slower direction. Backblaze’s documentation says later backups upload only new or changed files, and Apple says Time Machine backs up only the files that changed since the previous backup. Restores run the other way: Backblaze notes that restores over 1 TB may take several days, because the data must be prepared first.

The 3-2-1 rule

Keep three copies of any important file (one primary, two backups) on two different media types, with one copy offsite. US-CERT’s 2012 paper Data Backup Optionsstates the rule and cites photographer Peter Krogh’s The DAM Book.

Practical tips

  • Sync is not backup.Apple says iCloud “doesn’t back up your entire Mac”. Its Files app guide adds that deleting a file from iCloud Drive removes it from every device signed in with the same Apple Account, and that Recently Deleted keeps it for 30 days.
  • Plan for a bad day. Time Machine does not back up system files or apps installed with macOS, so a Mac with an empty disk needs macOS reinstalled first. Migration Assistant then restores your files, and Apple says large transfers might need hours.
  • Encrypt drives that leave home. Time Machine offers Encrypt Backup at setup, and you need the backup password to restore files.
  • A second disk can be your offsite copy if you keep it somewhere else. Time Machine rotates among disks and, for each, backs up what changed since it was last used.

What the planner does not do

  • It does not read your Mac, drives, or network. It works only from the numbers you type.
  • It does not run, monitor, or verify backups. The checklists record only what you tick, and only a real restore proves a backup works.
  • It cannot know how much your files really change, so the months figure is a direction, not a date.
  • Its restore time is download time only. It leaves out the provider’s preparation time and the time to reinstall macOS and move your files back.
  • It plans for Time Machine on a Mac, and it does not choose a backup service.

Frequently asked questions

Does Time Machine stop when the drive is full?

No. It deletes the oldest backups to make room for new ones. The cost is history: you can restore from fewer months back than you might expect.

Can I use a drive smaller than Apple recommends?

Yes, up to a point. Apple says you can keep backing up with a smaller disk, and Time Machine tells you when it needs more space. A drive smaller than your data cannot hold even the first full copy, and the planner flags that.

Why does the planner use decimal gigabytes?

Drive makers and speed tests count in decimal, and Apple’s storage-capacity page names only iOS 10 and earlier and OS X Leopard and earlier as examples of binary counting. The two units differ by about 7% at gigabyte scale, enough to tip a tight plan the wrong way, so the tool uses one unit throughout.

How often should I run a restore drill?

The tool suggests every three months, which is our suggestion rather than a standard. What matters is that you restore a real file and open it, so a failed backup shows up before you need it.

Related guides

Sources