How do I know if my fuel consumption rate is normal or high?

Average fuel consumption = Test mileage/ Total gallons of gasoline used during the test period
Let us use the following as an example:

Initial mileage is = 24,500mi
Final mileage is = 25,000mi

Test Mileage = (25,000-24,500)
Test Mileage = 500mi

I conducted this test for a 7-day period

Day 1 = 1 gallons
Day 2 = 2 gallons
Day 3 = 4 gallons
Day 4 = 3 gallons
Day 5 = 4 gallons
Day 6 = 2 gallons
Day 7 = 4 gallons

Total test gallons = ( 1 + 2 + 4 + 3 + 4 +2 +4)

Total test gallons = 20 gallons

Average fuel consumption = Test mileage/ Total Test gallons

Average fuel consumption = 500mi/20gallons

Average fuel consumption = 25miles/gallon

How do I know if this calculated average fuel consumption is right, is there an additional yardstick I could leverage?