IoU Calculator
Calculate the Intersection over Union score for object detection bounding boxes.
Inputs
IoU Score
0.2941
Union Area
170
Step by step
Union = Area A + Area B − Intersection
100 + 120 − 50
= 170
IoU = Intersection ÷ Union
50 ÷ 170
= 0.294118
How it works
Intersection over Union (IoU) measures how well a predicted bounding box overlaps with the ground truth. It equals the area of overlap divided by the total area covered by both boxes. An IoU ≥ 0.5 is typically considered a 'correct' detection in object detection benchmarks.
Formula
IoU
IoU = Intersection / Union = Intersection / (Area_A + Area_B - Intersection)
- Intersection
- Overlapping area between two bounding boxes
Frequently Asked Questions
What IoU threshold is standard for object detection?
PASCAL VOC uses 0.5, while COCO uses multiple thresholds (0.5 to 0.95 in steps of 0.05) for a more comprehensive evaluation called AP@[.5:.95].
Can IoU be used for segmentation?
Yes — for semantic/instance segmentation, IoU is computed over pixel-level masks rather than bounding boxes, and is also called the Jaccard index in that context.