What size inner tube would I need for a tire size4.80/4.00-8? It is for a garden cart.

Is this a trick question like who is buried in Grants tomb?

OK, you need one that is the size of the tire you will get a tube that is
4.80 / 4.00 - 8

eBay Store - Rustybore's Tire Store: 8 Tire Tubes: 16x6.50 7.50-8 Tire INNER TUBE for mowers and tractors (http://stores.ebay.com/Rustybores-Tire-Store_tire-Inner-tubes_8-Tire-Tubes_W0QQcolZ4QQdirZQ2d1QQfsubZ2480505QQftidZ2QQt Zkm)

http://doitbest.com/Wheelbarrow+wheels-Gleason+Corp.-model-09195-doitbest-sku-726806.dib

With that said, unless you are a pro at changing those tires, it is a pain to get that tube in there. So you may want to see if you can find a new tire just to replace that one.

What size inner tube would I need for a tire size4.80/4.00-8? It is for a garden cart.

Same size as the tire, 4.80 / 4.00 - 8