---
title: "How much storage does my Mac need? 256 GB vs 512 GB"
description: "Estimate the Mac storage you need from your photos, video, apps, games, Xcode and local AI models, with editable size assumptions and room left for macOS."
url: https://tidymac.space/tools/mac-storage-needed/
updated: 2026-10-16
---

[Home](/) [Tools](/tools/) Mac storage size calculator

# How much storage does my Mac need?

Add up what you keep on the Mac itself, add room for macOS, then leave about a fifth of the disk free. Move the sliders below; every size assumption is shown and editable.

Updated October 16, 2026By the Tidy Mac team

What you keep on the Mac

Photos kept on this Mac: **10 thousand photos**

**≈ 30 GB**AssumesMB per photo

Videos kept on this Mac: **5 hours of video**

**≈ 30 GB**AssumesGB per hour

Apps: **40 apps**

**≈ 20 GB**AssumesGB per app

Games: **0 games**

**≈ 0 GB**AssumesGB per game

Developer toolchains (Xcode, Android Studio, Docker): **0 toolchains**

**≈ 0 GB**AssumesGB each, with caches and simulators

Local AI models: **0 models**

**≈ 0 GB**AssumesGB per model

Music and podcasts downloaded offline: **1 thousand songs or episodes**

**≈ 8 GB**AssumesMB each

Documents and other files: **20 GB**

**≈ 20 GB**

macOS and System Data, roughly (GB)

Keep free (% of disk)

**168 GB**you’d store

**210 GB**with 20% kept free

**256 GB**recommended storage

Estimates from your inputs and the assumptions shown. The macOS and System Data figure starts at a rough 60 GB; System Data varies a lot between Macs, so set your own.

![](/img/brand/tidy-128.png)

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## How it works

Each row is **amount × typical size**. The typical sizes are assumptions, not measurements: change them to match your camera, your games or your models. The total adds your estimate for macOS and System Data, then divides by (1 − free space you want to keep), and picks the smallest of 256 GB, 512 GB, 1 TB, 2 TB that fits.

Storage sold as 512 GB is 512 decimal GB, the same units Finder uses (see the [GB to GiB converter](/tools/storage-unit-converter/)). Developer and AI workloads are usually the biggest surprise: read about [Xcode DerivedData](/learn/xcode-deriveddata/) and [local AI models](/learn/local-ai-models-ollama-lm-studio/).

## Questions

Is 256 GB enough for a Mac?

For web, email, documents and photos kept mostly in iCloud, often yes. Once you keep a large photo or video library on the Mac, install big games, use Xcode or run local AI models, it fills quickly. Move the sliders to see where your own use lands.

Where do the per-item sizes come from?

They are rough, typical assumptions for illustration, not measurements, and every one is editable. Photo, video and model sizes vary a lot with camera, resolution and format. If you have a Mac now, check real sizes in System Settings › General › Storage and enter those.

Why leave free space?

macOS needs room for updates, swap, caches and Time Machine snapshots, and System Data grows over time. A Mac that runs nearly full is the most common reason people search for [Mac storage full](/guides/mac-storage-full/). The calculator keeps 20% free by default; change it if you like.

Can I use iCloud or an external drive instead?

Yes. Optimise Mac Storage keeps only recent photos and files on the Mac, and big libraries can live on an external SSD. Set those sliders to what you keep on the Mac itself.

## Related

[Mac storage full? What to doGuide](/guides/mac-storage-full/)[Local AI models (Ollama, LM Studio)Library](/learn/local-ai-models-ollama-lm-studio/)[Xcode simulatorsLibrary](/learn/xcode-simulators-coresimulator/)[Steam games folderFolder](/folders/steam/)[Is it safe to delete?Free tool](/tools/is-it-safe-to-delete-mac/)[System Data explainerFree tool](/tools/system-data-explainer/)