Cake Pan Converter
Scale batter between round and square pans by area with time tips.
What it does
Swapping pans changes depth unless batter scales with area. An 8 inch round to a 9 inch round needs about 1.266 times the batter for the same layer height. Using the old amount gives a thinner, faster baking layer.
The tool above takes from and to shapes plus sizes and returns both areas and the scale factor. The defaults 8 in round to 9 in round match the worked example, so the page opens showing 1.266x. Switch to metric for centimeters.
Round area is pi x diameter squared / 4. Square area is side squared. Scale is to area over from area. Multiply batter, eggs, and leavening by scale for equal depth, then watch time: larger thinner layers bake faster, deeper layers slower.
Pans are not exact across brands. Measure inside top width for the truest area, since sloped sides widen at the rim. Fill half to two thirds to avoid overflow, and use strips or lower heat for deep sizes.
This page shows the formulas, one full hand checked example at 8 to 9 in round, a reference table, and practice checks that run through the tool in both unit systems.
How to use
- Pick Imperial (in) or Metric (cm).
- Pick from shape round or square.
- Pick to shape round or square.
- Type from size as diameter for round or side for square.
- Type to size the same way.
- Multiply batter by Scale for equal depth.
Formula
- d
- Inside diameter for round pans.
- side
- Inside side for square pans.
- scale
- Batter multiplier for equal depth.
Measure inside top for sloped pans. For equal depth, scale batter by area ratio. For same batter in a new pan, depth scales inverse to area.
Worked example
Example: 8 in round to 9 in round
Move batter from an 8 inch round to a 9 inch round at equal depth.
- From: pi x 8 squared / 4 = 50.2655 in2.
- Round: 50.27 in2.
- To: pi x 9 squared / 4 = 63.6173 in2.
- Round: 63.62 in2.
- Scale: 63.6173 / 50.2655 = 1.2656.
- Use 1.266x batter. Metric 20.32 to 22.86 cm gives the same.
Reference table
| Pan | Area | Scale vs 8 in round |
|---|---|---|
| 8 in round | 50.27 in2 | 1x |
| 9 in round | 63.62 in2 | 1.266x |
| 8 in square | 64 in2 | 1.273x |
| 9 in square | 81 in2 | 1.611x |
Limits
- Area only. Leavening and time shift with depth and shape.
- Sloped sides need top measure. Straight math assumes vertical walls.
- Fill limits ignored. Over two thirds risks overflow.
- Oven hot spots still need turning and testing.
Common mistakes
- Using diameter as radius, which quadruples error.
- Scaling by diameter ratio instead of area ratio.
- Keeping time fixed when depth changes a lot.
- Measuring outside pan instead of inside top.
- Filling small pans to the rim with scaled batter.
Try it yourself
Quick checks. Answers sit tucked under each question.
8 in square to 9 in round?
From 64 in2 to 63.62 in2, scale 0.994x.
9 in round to 8 in square?
From 63.62 in2 to 64 in2, scale 1.006x.
Questions
8 to 9 in round scale?
1.266x batter for equal depth.
Round or square bigger?
Compare areas. 8 in square at 64 beats 9 in round at 63.62.
Same batter, new pan?
Depth changes inverse to area. Larger pan gives thinner layer.
Time change?
Thinner bakes faster, deeper slower. Test early with a pick.
Measure where?
Inside top edge for the truest baking area.
Metric?
Same ratios. 20.32 to 22.86 cm gives 1.266x.