Converting Recipes Between Metric and Imperial Pan Sizes

Many baking recipes use metric measurements while American kitchens typically use imperial pan sizes. Converting between metric and imperial pan sizes requires understanding both measurement systems and adjusting recipes accurately. This guide explains the conversion process and provides practical strategies for adapting international recipes.

Use our Baking Pan Size Converter to easily convert between metric and imperial pan sizes with precise calculations.

Understanding Metric vs. Imperial Pan Sizes

Metric baking pans are measured in centimeters and milliliters, while imperial pans use inches and cups. European and Australian recipes commonly specify metric dimensions, while American recipes use imperial measurements. Understanding both systems helps you adapt recipes from any source.

Metric Pan Sizes: Typically measured in centimeters (cm) for dimensions and milliliters (mL) or liters (L) for volume. Common sizes include 20cm round, 18cm square, or 20×30cm rectangular pans.

Imperial Pan Sizes: Measured in inches (") for dimensions. Standard sizes include 8" round, 9×13" rectangular, or descriptions like "9-inch square."

Volume Differences: Metric recipes may specify pan capacity in milliliters or liters, while imperial recipes often describe pan dimensions. Converting requires calculating volumes from dimensions.

Common Metric Pan Sizes and Imperial Equivalents

Knowing standard metric sizes and their closest imperial matches simplifies conversions:

Round Pans:

• 18cm round ≈ 7" round (slightly smaller)
• 20cm round ≈ 8" round (very close)
• 23cm round ≈ 9" round (slightly smaller)
• 26cm round ≈ 10" round (very close)

Square Pans:

• 18cm square ≈ 7" square (slightly smaller)
• 20cm square ≈ 8" square (very close)
• 23cm square ≈ 9" square (slightly smaller)

Rectangular Pans:

• 20×30cm ≈ 8×12" (slightly larger than standard 9×13")
• 18×28cm ≈ 7×11" (close to 8×11")
• 30×40cm ≈ 12×16" (much larger, commercial size)

Bundt Pans:

• 1.5L capacity ≈ 6 cup bundt
• 2.4L capacity ≈ 10 cup bundt
• 2.8L capacity ≈ 12 cup bundt

Conversion Calculation Methods

Converting pan sizes requires calculating volumes in both systems:

Step 1: Convert Dimensions: Use conversion factor 1 inch = 2.54 cm. For example, 20cm ÷ 2.54 = 7.87" ≈ 8".

Step 2: Calculate Volumes: Use standard formulas:

• Round: π × r² × h (radius and height in same units)
• Square/Rectangular: length × width × height
• Convert cm³ to cubic inches: 1 cm³ ≈ 0.061 cubic inches

Step 3: Compare Volumes: Calculate volumes in both systems and find the closest match. Small differences (within 10%) are usually acceptable.

Step 4: Adjust Recipe: Scale ingredients proportionally based on volume ratios.

Practical Conversion Examples

Here are common conversion scenarios:

20cm Round to Imperial: 20cm = 7.87" ≈ 8". Volume: π × (10cm)² × 5cm ≈ 1,571 cm³. An 8" round pan holds about 100 cubic inches ≈ 1,639 cm³. These are very close—nearly interchangeable.

23cm Square to Imperial: 23cm = 9.06" ≈ 9". Volume: 23 × 23 × 5cm ≈ 2,645 cm³. A 9" square pan holds about 162 cubic inches ≈ 2,654 cm³. Perfect match.

20×30cm Rectangular: 20cm = 7.87", 30cm = 11.81". Volume: 20 × 30 × 5cm = 3,000 cm³. A 9×13" pan (234 cubic inches ≈ 3,834 cm³) is larger. An 8×12" pan would be closer but less common.

Handling Volume-Based Recipes

Some metric recipes specify pan capacity rather than dimensions:

Liters to Cups: 1 liter = 4.22675 cups. A 2L pan capacity ≈ 8.5 cups.

Milliliters to Cups: 1 mL = 0.004227 cups. 500mL ≈ 2.1 cups.

Capacity vs. Dimensions: Pan capacity refers to liquid volume, while baking uses batter volume (similar but not identical). Use capacity as a guide, but calculate from dimensions for precision.

Ingredient Conversion Considerations

When converting recipes, ingredients may also need conversion:

Weight Measurements: Metric recipes often use grams, while imperial uses cups. Convert flour: 1 cup ≈ 120-125g, sugar: 1 cup ≈ 200g.

Liquid Measurements: 1 cup = 240mL. Metric recipes may specify milliliters directly.

Temperature: Metric recipes use Celsius. Convert: C = (F - 32) × 5/9.

Baking Time: Usually remains similar, but check for doneness using standard methods rather than relying solely on time.

Common Conversion Challenges

Several challenges arise when converting between systems:

Rounding Differences: Small rounding differences accumulate. Always calculate volumes precisely rather than relying on approximate dimension matches.

Pan Depth Variations: Metric pans may have different standard depths (5cm vs. 2 inches). Account for depth differences in volume calculations.

Recipe Scaling: Converting pan sizes often requires scaling ingredients. Be precise with conversions to maintain recipe ratios.

Oven Temperature: Different countries may use different oven temperature standards. Verify conversions are accurate.

Finding Equivalent Pans

When you don't have exact metric equivalents:

Use Closest Standard Size: Choose the imperial pan closest in volume. Small differences (within 10%) rarely matter significantly.

Calculate Volume Ratio: Determine the volume difference and scale recipe accordingly. For example, if target pan is 15% larger, increase ingredients by 15%.

Consider Recipe Flexibility: Some recipes are more forgiving than others. Cakes may need precise sizing, while brownies adapt easily.

Test First: When possible, test conversions with small batches before committing to full recipes.

Adapting International Recipes

Many excellent baking recipes come from metric-using countries:

European Recipes: Often specify centimeter dimensions. Convert to closest inch equivalents and adjust recipe quantities.

Australian Recipes: Use metric measurements with some unique pan sizes. Convert dimensions and ingredients carefully.

British Recipes: May use both systems. Check whether dimensions are metric or imperial before converting.

Asian Recipes: Often use metric measurements. Follow conversion process systematically.

Practical Tips for Success

These strategies improve conversion success:

Document Conversions: Keep notes on successful conversions for future reference. Build your personal conversion database.

Start Conservative: Use slightly smaller pans initially and adjust upward if needed. Easier to scale up than down.

Check Multiple Sources: Compare conversion factors from multiple sources to verify accuracy.

Understand Recipe Context: Some recipes specify pan sizes for structural reasons (like certain cake types). Research recipe requirements before converting.

Test Small Batches: When possible, test conversions with smaller batches or half recipes before full commitment.

The Bottom Line

Converting between metric and imperial pan sizes requires systematic calculation of volumes and careful recipe scaling. Use precise conversion factors, calculate volumes accurately, and scale ingredients proportionally. Small differences (within 10%) are usually acceptable, but precision matters for delicate recipes.

Use our Baking Pan Size Converter to handle these conversions automatically. With practice, you'll develop confidence adapting recipes from any measurement system to match your available equipment.

Frequently Asked Questions

How do I convert a 20cm round pan recipe to imperial? 20cm ≈ 8". Calculate volumes precisely: 20cm round ≈ 1,571 cm³, 8" round ≈ 1,639 cm³. They're very close—nearly interchangeable.

What's the closest imperial size to a 23cm square pan? 23cm ≈ 9". A 9" square pan is the closest match with nearly identical volume.

Do I need to convert ingredient measurements too? Yes, if the recipe uses metric measurements. Convert weights (grams to cups) and volumes (mL to cups) accurately.

Can I use a slightly different pan size? Usually yes, within 10% volume difference. Adjust recipe quantities proportionally and monitor baking time.

Citations

• King Arthur Baking. "Metric to Imperial Baking Conversions." KingArthurBaking.com.
• Joy of Baking. "Converting International Recipe Measurements." JoyofBaking.com.
• NIST. "Metric Conversion Guidelines." NIST.gov.