Dimension Out of Range Debugger
Debug PyTorch IndexError: Dimension out of range. Enter tensor shape and the dimension index to see valid ranges and fix the error.
Built by Michael Lip
Frequently Asked Questions
What does Dimension out of range mean?
You tried to access a dimension that doesn't exist. A 3D tensor has dimensions 0, 1, 2 (or -1, -2, -3). Accessing dimension 3 or -4 triggers this error. Valid range: [-ndim, ndim-1].
How does negative dimension indexing work?
Negative indices count from the last dimension. dim=-1 is the last, dim=-2 is second to last. Same convention as Python list indexing.
Common causes?
(1) Using dim=1 on a 1D tensor. (2) Squeeze removed a dimension. (3) Hardcoded dim values after reshape. (4) Confusing dim with dimension size.
How do I fix it?
Print tensor.shape to see actual dimensions. Adjust dim to be within [-ndim, ndim-1]. Use unsqueeze if you need more dimensions.
Is this tool free?
Yes. All HeyTensor tools are free, run in your browser, and require no signup.
About This Tool
Part of HeyTensor. All calculations run in your browser. Source code on GitHub.
Contact
Built by Michael Lip. Email [email protected].
TENSOR PREFLIGHT · DOWNLOADABLE PYTORCH TOOLKIT
Take the next step in your own PyTorch model.
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Use the free calculator for a layer formula or a quick shape check.
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Python 3.9+ · PyTorch 2.8+ · Runs locally