21 US gallons in imperial gallons

Conversion formula
How to convert 21 US gallons to imperial gallons?

We know (by definition) that: $1\mathrm{usgallon}\approx 0.832674184628989\mathrm{imperialgallon}$

We can set up a proportion to solve for the number of imperial gallons.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 21 ⁢ usgallon ≈ 17.48615787720877 ⁢ imperialgallon

Conversion in the opposite direction

The inverse of the conversion factor is that 1 imperial gallon is equal to 0.0571880916907074 times 21 US gallons.

It can also be expressed as: 21 US gallons is equal to $\frac{1}{\mathrm{0.0571880916907074}}$ imperial gallons.

Approximation

An approximate numerical result would be: twenty-one US gallons is about seventeen point four eight imperial gallons, or alternatively, a imperial gallon is about zero point zero six times twenty-one US gallons.