It's probably slightly above average for a family of 3 but it depends why you're asking.
What others spend and how much you do don't necessarily compare because everyone has different budgets, requirements and priorities. People also spend different amounts on takeaways or lunches so this needs to be part of the consideration, also what shops you have access to.
If you can use Aldi, Lidl or Asda, or can buy your cleaning and toiletries in a bargain shop, you'll get away with spending less than if your only options are Waitrose, Sainsbury's and Tesco.
If you can easily afford it, aren't wasting food and just need an amount to demonstrate to DH that groceries cost money, it's fine.
If you're on a low income and need to free up money for increased utility bills, to be able to save for other irregular expenses or waste a lot of what you buy, then you probably could knock a little off the budget.
If the reason you're asking is because your DH thinks you spend too much, there's two options.
You either make savings by cutting out things he likes but you and DC are less bothered about, often lots of meat or snacks.
Or you put him in charge of meal planning, food shopping and keeping the house stocked with essentials such as toilet paper and laundry detergent.