How to use the Microwave Cubic Feet Calculator
- Measure the inside cavity, keeping wall thickness and the external housing outside the calculation.
- Enter the inside cavity dimensions. Subtract a separately measured excluded volume if relevant.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Microwave formula
The rectangular interior envelope gives gross volume. Subtract the entered excluded volume to estimate net capacity.
Usable volume ≈ interior length × width × height − excluded volume
What the terms mean
- Interior length
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Interior width
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Interior height / depth
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Excluded interior volume
- Entered in ft³.
Microwave worked examples
Estimate a rectangular microwave cavity
The interior cavity measures 14 in × 14 in × 9 in. Assume no separately measured excluded volume.
- Interior length × width × height − excluded volume
Answer: 1.020833 ft³. Cubic yards: 0.037809 yd³; Litres: 28.906781 L; Gross interior volume: 1.020833 ft³.
Subtract an interior obstruction
The cavity measures 16 in × 15 in × 10 in. Subtract a measured 0.05 ft³ obstruction.
- Interior length × width × height − excluded volume
Answer: 1.338889 ft³. Cubic yards: 0.049588 yd³; Litres: 37.913111 L; Gross interior volume: 1.388889 ft³.
Microwave Cubic Feet Calculator FAQs
Is the turntable diameter the cavity width?
No. Measure cavity width separately. The turntable diameter helps check dish clearance, not full rectangular capacity.
Why can my estimate differ from the advertised size?
Manufacturer capacity may use a different measurement procedure or account for shapes that a rectangular estimate does not.
Measurement guide for Microwave
Measure usable internal width, depth and height. Check dish dimensions separately because a cubic-foot capacity does not establish turntable clearance.
Assumptions and limits
Rounded corners, liners and turntable geometry affect usable space. A dish also needs clearance; cubic capacity alone does not prove it will fit.
Interior dimensions give an estimate. Shelves, liners and curved surfaces may differ from the manufacturer’s tested capacity.
Check your result
Compare gross cavity volume with the excluded volume. Capacity is approximate where the cavity is curved or obstructed.