IoU Calculator
Calculate the Intersection over Union score for object detection bounding boxes.
About IoU Calculator
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
Worked example
With the default values below, IoU Calculator returns IoU Score of 0.2941. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Intersection Areaminimum 0
- 50
- Box A Areaminimum 1
- 100
- Box B Areaminimum 1
- 120
Results
- IoU Score
- 0.2941
- Union Area
- 170
Step by step
- 1Union = Area A + Area B − Intersection= 170
- 2IoU = Intersection ÷ Union= 0.294118
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.