How this calculator works
A price index compares the cost of a basket of goods with the same basket at a reference place or time. Here the basket is a single beach day: sunscreen, drinks, beer, ice cream, lunch and any facility or parking fee. Adding the six items gives the cost of the day, and dividing by the hours spent there gives an hourly rate that is fair to compare between a short swim and a long afternoon. The reference beach cost is treated as 100, so a day that costs 57 against a 50 reference has an index of 114, meaning 14 percent more expensive.
Formula
Cost of the day = sunscreen + water + beer + ice cream + lunch + facility fee. Cost per hour = cost of the day / hours at the beach. Difference = cost of the day - reference cost. Index = cost of the day / reference cost, displayed as a percentage.
Worked example
Sunscreen at 8, water at 3, beer at 8, ice cream at 5, lunch at 18 and a 5 facility fee add up to 47 for a six hour visit. That is 7.83 an hour. Against a reference beach that costs 50, the difference is -3 and the index is 94 percent, so this beach is six percent cheaper.
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Frequently asked questions
What belongs in the facility fee?
Use it for anything you must pay to be there: parking, an entry charge, a beach umbrella rental or a locker. Travel to the beach is not included, so that a distant free beach is not made to look cheaper than it is.
Why divide by hours instead of by people?
The index compares the cost of a day, not a per-person price. Dividing by hours shows how efficiently the money is spent over the visit, while the day total stays comparable with another beach regardless of how long you stay.
What does an index of 100 mean?
The day costs exactly the same as the reference. Anything below 100 is cheaper and anything above is more expensive; 120 means 20 percent more. The calculator also shows the cash difference, which is often easier to act on.
Is this the same as a consumer price index?
It uses the same idea of comparing a fixed basket with a base period, but the basket here is a fun day out and the base is another beach. It is not a national statistic and should be treated as a personal comparison, not an economic measure.