The dilution of the spray will be dependent on your target weed and the particular formulation you have. Here's a link to read the Round Up Original label. If it is not this one, you can find the correct label online.

Here is a link that might be useful: Round up original label

I have lost my instructions on how much roundup to use in a gallon of water. Please e-mail me.

I left my round up in the sun for weeks if a plastic bag and it still works fine so I'm sure yours will work fine too. Maybe just shake it up so that it mixes well. My instructions got wet and ruined but I looked it up online and it believe it is 5 tablespoons per gallon of water. I do that and mix in some dish soap and its been working for me.

please do not use roundup. It is a chemical that harms the soil and ground water. Please try instead using vineagar. It does not harm the soil and has been proven to kill weeds. All you need to do is spray it on directly to the weeds. You can use a spray bottle no need to dilute the vineagar. You could also try poring hot water on your weeds. That is a free and easy way to get rid of weeds.