# How to Calculate Fold

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A calculator can help determine change in amounts.

A fold change is basically a ratio. It indicates the number of times something has changed in comparison to an original amount. A twofold increase indicates that an amount doubled. Fold change is useful in examining data for increases and decreases.

## Step 1

Divide the new amount of an item by the original amount to determine the fold change for an increase. For instance, if you have 2 armadillos in a hutch and after breeding, you have 8 armadillos, the calculation is 8/2 = 4. The 4 means that you have a 4-fold increase in the number of armadillos.

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## Step 2

Divide the original amount by the new amount to determine the fold change for a decrease. For instance, if you have 20 grams of water at the beginning of an experiment and end up with 4 grams, divide the original number (20) by the new (4) and note the answer as a negative result. In this case, 20/4 = -5 fold.