"The startup disk does not have enough space to be partitioned." error in Boot Camp Assistant.

I restored my MacBook to 10.15 Catalina. Im trying to install Windows 10 build 1507, but it keeps giving me "You must have at least 41 GB of free space available."and it might occur because the partition would be too small. But I have at least 87.12 GB of space available.Please help me why it keeps giving me this error.

MacBook Air 13″

Posted on Jun 30, 2025 2:49 PM

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Posted on Jul 3, 2025 9:32 AM

With a 120GB SSD (yes it may show up as 128GB SSD, but only 120GB is actually usable). You really don't have a large enough internal SSD to dual boot. You need at least a 250GB internal SSD.


With macOS Available storage is unfortunately very misleading storage value. You need to use Disk Utility to check how much actual Free storage space you have. Unfortunately Free is not synonymous with Available in this context.


IIRC, you may need about 65GB+ or so just for the Windows installation. You should always have at least 20GB+ of Free space for macOS, but should have 20%+ of Free storage at all times since that 20GB can disappear very quickly even with simple tasks.


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Question marked as Top-ranking reply

Jul 3, 2025 9:32 AM in response to Ycode

With a 120GB SSD (yes it may show up as 128GB SSD, but only 120GB is actually usable). You really don't have a large enough internal SSD to dual boot. You need at least a 250GB internal SSD.


With macOS Available storage is unfortunately very misleading storage value. You need to use Disk Utility to check how much actual Free storage space you have. Unfortunately Free is not synonymous with Available in this context.


IIRC, you may need about 65GB+ or so just for the Windows installation. You should always have at least 20GB+ of Free space for macOS, but should have 20%+ of Free storage at all times since that 20GB can disappear very quickly even with simple tasks.


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"The startup disk does not have enough space to be partitioned." error in Boot Camp Assistant.

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