This sucks being a noob again at something , Im sure this is a very common question.

I'll be doing a fixed gear conversion to my 70's schwinn varsity I got for free. I'm not ******** when it comes to these things and mechanics, but still have much to learn.

Where I live it is all very flat, except for one incline which is maybe a quarter mile long and 10-20 degree angle. Im young and pretty in shape but just want to be sure to make it up this hill without killing myself, and without additional gears. Im going to try it on my friends bike today, hopefully he knows what gearing he has.

Any direction would be great.

If there is a hill with a 10-20 degree angle I would move.
Honestly there isn't a fixed gearing that will let you go fast on the flats without spinning out AND climb a 10 degree hill. Or am I thinking a 10% hill. Never mind.

This question has been answered ad infinitum so search for more info..
Since I was a dick in the first paragraph... go with 70 gear inches.
Here's the link...

https://www.bikeforums.net/singlespeed-fixed-gear/468351-gearing-primer.html

i live in davis ca (all flat except the occasional bike trail tunnels) and i run 48x17 (front gear teeth x rear gear teeth). 17 skid patches. skidable, not sure if i can wheelie tho~

thanks for the input so far, its starting to make sense now and fall in place.

70 gear inches seems good, I just have to figure out the # of teeth for the chain ring and cog. Im looking at a 165mm lenth crank.

Still trying to figure out the effect of raising or lowering the teeth on the chaing ring vs the cog, and while still keeping it around 70 gear inches.

I believe I also read that I want to keep the one number of teeth even and the other odd (I may have mis read something there).

im a nub at gear inches~ what does it actually translate to? like longer the gear inch the harder to pedal? im at 48x17 so that sets me at 76.2 gear inches~ what does that mean if i were to go down or go up in inches?

Higher number is harder, lower number is easier.

If you want different gearing change the cog, it's cheaper and if you have a fixed/fixed hub you can rock 2 different ratios easily.

something like 46x18 would work well for you

This is some golden advice, thanks tmh!

i keep around 70 gear inches

+1. i find 70-75 GI to be good for general street use.

I'm running 70.5 GI with a 47x18 setup. I have about 70% flat land and plenty of steep inclines here, I can get up them without a problem.

Just found out I was riding my friends bike on Sat with 86 G.I. I can say from first impression I thought it seemed a bit "tough" to get going. I would say not a start/stop or hill bike for me anyway.

I run a 46x15 in Austin (lots of steep hills) but I was a road biker before I started riding fixed, so I have pretty strong legs. I am, however, going to switch my cog to a 16t one b/c I just got this Soma cog for 10 bucks off ebay, so I might as well and it would probably make things a little bit easier.

When I started (in SF mind you), I used a 45x19 combo, then graduated to a 45x17, then to a 52x19.

Take your gear inch number and multiply by 3.14 to get an idea of actual travel distance. For instance, 52x19 combo gives about a 72 gear inch and a 226 inch development. about 18'-10" of travel per rotation.

I'd say mid 60s would be good to introduce yourself to riding fixed, and lower 70s would be a good graduation point.

my kilo tt came with 48x16 so thats 81 inches, and then i moved onto 48x17 (76.2")~ so should i go back down to lower gears? (is it like a knee health issue? or should i try to totally change up my gears so i get ~low 70's?)

You went from a 3 to 1 ratio to a 2.8 to 1 ratio which means it should now be easier to pedal (your distance per rotation went from about 21'-2" per pedal revolution down to around 19'-10" per revolution).

The higher your ratio, the more difficult to get started at full stops, the harder to skid, which translates into more stress on your knees. I'm not sure what you're asking, if you like 48x17, then great, stick with it, if you want an easier ride, then you'll want to put on an 18 or 19 tooth rear cog.

I find low 70s to be very agreeable with frequent full stop to starts and very responsive to getting into skips and skids without over-exerting myself. But I max out at a lower top speed because of it.

Well to start, a "10-20 degree angle" is a really wide range. For reference, here's a 21 degree hill in Seattle: Linky. If you can get up your hill with 48x17, I doubt it's that steep. If it is actually that steep, then you'll have to consider the length of the ride you're doing, and just walk that portion, or find a route around it. If you're able to ride it with what you've got, then just consider whether you're comfortable with however hard to have to peddle (keeping in mind your shape, and that it'll get easier if you keep doing it).

Personally I use 46x17 which I've found just perfect for the fairly hilly (but not super steep) area of north Seattle (and fairly fast on the flats), but I do have to walk if I hit some super steep hill (not very many, most hills are fairly short and I can just power through it).

I thought riding fixed was for people who DIDN'T want to have to worry about gear ratios. I run a pretty tough ratio, and when I see a big hill coming I just power through it. Try doing that. If it's really tough, I'll mumble to myself: "I think I can, I think I can, I think I can, I think I can..."

lol i vote for just trying a ratio if you cant make it up the hill trade someone cogs and try again.