Just how earthlike is the planet? Assume it is a shirtsleeves environment for humans, at least in the nice spots ...
- Assuming dehydrated/dry food, with a few supplements, it should be possible to live on less than 1 kg of food per day. Double that for sundries like toilet paper, aspirins, or new socks. 730 kg for one year. (If the world is reasonably Earthlike, the growing seasons should have about the same length.)
- 250 kg per person should be plenty for a sturdy all-weather tent, camping cot, sleeping bag, stuff like that.
So with one ton, your colonist can live for a year.
Say the colonists want to clear fields, put seeds into the ground, and get a bountiful harvest.
- The interior of a standard athletic track is one hektar (ha). Modern grains might required 100 kg of seed for 1 ha, and yield several tons of grain on Earth. Your alien world will have unknown pests and other calamities.
- The figure assumes modern mechanized agriculture.
Still, an off-the-cuff estimate suggests that your colonists should be able to feed themselves with starchy staple foods after the first growing season, if Earth grains will grow. For the second year, the colonist will need much less than a ton -- perhaps some vitamin or mineral supplements, and the occasional imported chocolate bar from home.
Note that I haven't suggested cars, or tractors, or aircraft. Decide on the ratio of jeeps or tractors per colonist. A well-supplied colony could have close to one vehicle per colonist. A bare-bones colony could have less than one vehicle for every 10 or even 100 colonists. Say an average farm has 200 workers and perhaps a dozen vehicles: a few tractors, a few trucks, perhaps a combine harvester.
An off-the-cuff estimate says less than 1 ton of vehicle per colonist. How much fuel and spare parts per vehicle? Unless they will find a way to make fuel locally, bringing vehicles makes no sense at all, so it will be just a little initial stock, until the oil wells and refineries, or solar farms and electrolysis systems, or soyfields and biodiesel refineries are set up.
Other workers will require their own "tools of the trade." Machine shops, hospitals, whatever. Assume that those, too are 1 ton per worker.
That suggests a ratio of 2 tons of cargo for each colonist.
But I made some very back of the envelope estimates here. What is the goal of the colony? Become a self-sufficient technological society as fast as possible? Become a genetically healthy human society as fast as possible? Living room for the crowded masses of the homeworld?
I think anything from 1 ton per colonist to 10 tons per colonists can be justified.