Generally speaking, you will want to thin the paint by 10%, or for every gallon of paint, you will want a quarter cup of water or thinner. This is what is recommended for emulsion, acrylic, and latex paint, but we always recommend checking on the label of your paint and your spray gun’s instructions, as sometimes they can suggest different quantities. It is always best to follow the guidance on the spray gun to avoid overloading it with thick paint, as that can damage the gun and leave you with chunky paint, which no one wants! For those using an airless sprayer, you will want to increase the water by 20 or 30%. You can do this by adding more water or thinner to the paint, increasing the ratio that we suggested above. You will also want to consider the surface that you are spraying the paint on. If it is an absorbent surface, then you will want to add more water. For example, if you are using acrylic on an absorbent surface, you could add 50% water to thin the paint. For other surfaces, you will want to keep it below 30% as we suggested earlier. You will want to carefully consider the type of paint you are using and the surface that you are painting to ensure that you get the ratio correct. If you run into any issues, we recommend speaking to a professional who can offer you more tailored advice.