How To Reduce A Cake Recipe To Fit A Smaller Sized Tin


Use my formula & examples, to reduce a recipe to fit a smaller sized cake pan.  See how to adjust ingredients accurately for no fails.  Use for cakes, pastry etc.  Anywhere, you need to reduce a recipe for a smaller size of pan or dish.   Example being, the recipe uses a 8" cake pan, but you have a 6" pan.

Since I am often asked how to reduce a recipe to fit a smaller cake tin, I decided to provide you with the formulas to make it simple for you to reduce your ingredients.  I also have an article on How To Increase A Recipe For A Bigger Sized Dish.


Type & Size Of Cake & Pie Tins Included

So I have listed standard cake shapes and sizes I believe are available here in the  UK & in the states and Canada.  If you know of anymore I missed, please get in contact via the website of Facebook and I will gladly update it.  

How To Use The Formulae

At the end of the formulae (formulas), I will give some examples so everyone is clear how to do this, either using the % button on a calculator (or more realistically your phone), or by multiplying by the relevant decimal (and I will refer to it as a ‘factor’).  

Not A Whole Number

When it comes to not a whole number, here’s an example – if the answer for say flour is 258.61 g, then round to 259g.  (When the number after the decimal point is 5 or higher, you round up to next whole number.  And if less than 5, reduce to the next lowest whole number).  So  374.21g would be 374g.  When it comes to eggs, use your judgement if it’s not a whole number.  The size of the egg will also play a part in this.  Adding half or 1/4 of an egg more, will not make too much difference.  


Round & Square Tins

Note that reducing from a round tin to a smaller round tin, has the same formula for reducing from a square tin to another smaller square tin.  So the formulas below do not apply for changing tin shape.  

Using Cups

At the end I will also discuss how to reduce your ingredients when using cups instead of grams or ounces.  

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Video Demonstration

Here’s a video of me doing the calculations, using my tables


Formulae For Reducing Recipes

ROUND & SQUARE – 8″ (20.3cm)

Original recipe uses 8″ (20.3cm) Tin:

REDUCE TO TINMULTIPLY BY
7″ (17.8CM)79% or 0.79
6″ (15.2cm)57% or 0.57
5″ (12.7cm)40% or 0.40
4″ (10.1cm)24% or 0.24
Reducing From A 8″ (20cm) Tin

Examples:

  •  425g flour  –  425 x 0.57 (57%) =  242.25g becomes 242g

  • 4 eggs  –  4 x 0.79 (79%) = 3.16 so use 3 eggs

  • 2 tsp baking powder – Think of 2 tsp as same as 16 x 1/8 tsp
  • So  16 x 0.57 (57%) = 9.12  & round down to 9
  • And 9/8 tsp is the same as 1 + 1/8 tsp which is easier to use.
  • If you don’t have an 1/8 tsp, just half fill a 1/4 tsp**
  • ***You can also skip the converting to 1/8tsp if you are good with small fractions & just calculate ‘2 x 0.57 = 1.14 tsp’. But for most, 0.14tsp is not a known factor. See below.

METHOD 2 FOR CALCULATING

You can use a calculator and just multiply my factor (the decimal or % in the tables), by the ingredient amount.

  • 2 tsp x 0.57 = 1.14 but what is 0.14 tsp in a fraction?
  • Method 1 – 16 x 0.57 /8 = 9.12/8 = 9/8, which you can reduce to 1 1/8 tsp.

  • More Examples
  • 1 1/2 tsp baking soda  – Same as 12 x 1/8 tsp 
  • Factor = 24% or 0.24, example being reducing from 8″-4″
  • Method 2 – 1.5 x 0.24 =0.36 =1/3 tsp, & difficult to measure
  • Method 1 –12 x 0.24 (24%) = 2.88 (2.88/8)
  • I would round up to 3 & divide by 8 = 3/8 which means 3 x 1/8 tsp or 1/4 tsp + 1/8 tsp

  • 240ml Veg Oil  –  240 x 0.57 (57%) = 136.8ml
  • I would use 135ml for easier measuring on a jug. If using the ml unit on digital scales, you could use 137ml.
  • For cup sizes I will explain further down the article.


ROUND & SQUARE – 7″ (17.8cm)

Original recipe uses 7″ (17.8cm) Tin:

REDUCE TO TINMULTIPLY BY
6″ (15.2cm)72% or 0.72 
5″ (12.7cm)50% or 0.50
4″ (10.1cm)70% or 0.70
Reducing from a 7″ (17.8cm) tin

ROUND & SQUARE – 9″ (22.8cm)

Original recipe uses 9″ (22.8cm) Tin:

REDUCE TO TINMULTIPLY BY
8″ (20.3cm)77.5% or 0.775
7″ (17.8cm)61% or 0.61
6″ (15.2cm)44% or 0.44
5″ (12.7cm)31% or 0.31
4″ (10.1cm)19% or 0.19
Reducing from 9″ (22.8cm) tin

ROUND & SQUARE – 10″ (25.4cm)

Original recipe uses 10″ (25.4cm) Tin:

REDUCE TO TINMULTIPLY BY
9″ (22.8cm)82% or 0.82
8″ (20.3cm)63.5% or 0.635
7″ (17.8cm)50% or 0.5
6″ (15.2cm)36% or 0.36
5″ (12.7cm)25% or 0.25
4″ (10.1cm)15% or 0.15
Reducing from a 10″ (25.4cm) Tin

ROUND & SQUARE – 11″ (27.9cm)

Original recipe uses 11″ (27.9cm) Tin:

REDUCE TO TINMULTIPLY BY
10″ (25.4cm)82% or 0.82
9″ (22.8cm)67% or 0.67
8″ (20.3cm)52% or 0.52
7″ (17.8cm)41% or 0.41
6″ (15.2cm)  30% or 0.30
5″ (12.7cm)21% or 0.21
4″ (10.1cm)13% or 0.13
Reducing from a 11″ (27.9cm) tin


REDUCING WITH MEASURING CUPS

For measuring cups it’s not quite as easy, so purchasing an inexpensive digital scale, would be easier and actually more accurate.  Most come with grams and ounces as standard measurement units.  There is maths involved here with reducing cups, but here’s some examples to guide you.

Cup Examples

The smallest cup size is 1/8 cup & so using that we can reduce the size using cups.  

•To reduce 4 cups flour to 15% of the original,

  think of 4 cups as the same as 32 x 1/8 cups (ie. 8×4=32)

 Then 32 x 0.15 (15%) = 4.8 and round up to 5

 This means 5 x 1/8 cups, which also is 2/3 cup.

**(note – 5/8=0.625 which is close to 2/3= 0.66)


  • 4 cups again, but reducing using 0.24
  • 32 x 0.24 (24%) = 7.7 & round up to 8 = 1 cup
  • (ie. 8/8 = 1 so 1 cup)

  • 4 cups & reducing by 0.31
  • 32 x 0.31 (31%) = 9.9 & round up to 10
  •   This means 10/8 c = 1 & 2/8 c = 1 & 1/4 cup

32 x 0.40 (40%) = 12.8 so round up to 13

  This means 13/8 c = 1 & 5/8 c or a bit more than 4/8 cup = 1/2 cup. So say little over 1/2 cup


32 x 0.57 (57%) = 18.24 so round down to 18

  This means 18/8 = 2 & 2/8 c = 2 & 1/4 cups


32 x 0.79 (79%) = 25.28 so round down to 25

  This means 25/8 = 3 & 1/8 cup


You could also use based on 1/4 cup sizes, but this will be less accurate.  

**For info, for flour – 1tsp is approximately 1/5 of a 1/8 cup. 



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DECREASING SQUARE 12 ” TO A RECTANGULAR 9X 13

To reduce a 12″ (30.5cm) square tin to fit a 9 x 13″ (23 x 33 cm) rectangular dish (when both the same depth) –

• Reduce by 18.5%, therefore multiply by 0.815 (81.5%)

Example:

• reducing 4 cups 

  multiply 32 x 0.815 (81.5%) = 26/8

  & equals 3 & 2/8 = 3 & 1/4 cups


 • And in grams

  500g x 0.815 (81.5%) = 407.5g = 408g 


Hope this helps.  If there are any errors or anything missing, please get in contact. I also have an article on how to adjust a recipe for a bigger dish size.

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