Is my math correct for SPH, MPH and KPH?

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#1

So I am making a car system and I want to display speed in SPH, MPH and KPH. Are they correct? if not how can I fix my formulas for them? I am pretty sure that one of my formulas is wrong, so I need some help.

-- x variable contains Part.Velocity.Magnitude

local function toSPH(x)
	return x -- I am not sure what to do here, I tried multiplying by 3600, but thats not correct. I am missing something
end

local function toMPH(x)
	return (x / 1609.344 / 3.571 * 3600) -- is this correct?
end

local function toKPH(x)
	return x * (20000 / 3600) -- is this correct too?
end
1 Like
You can now convert SPS to MPH!
#2

A Part’s velocity is studs per second, so for studs per hour yes you would multiply by 3600.

local function toSPH(x)
--[[
studs     3600 seconds   studs
------- * ------------ = -----
seconds   1 hour         hour
]]
	return x * 3600
end

For the others it depends on the coefficient you use to convert studs to miles or kilometers.

local function toMPH(x)
--[[
let M be the conversion factor of studs per mile

	studs     3600 seconds   1 mile    miles
	------- * ------------ * ------- = -----
	seconds   1 hour         M studs   hour
]]
	return x * 3600 / M
	-- OR do this:
	return toSPH(x) / M
end

Then converting to km/hour is easier:

local function toKPH(x)
	return toMPH(x) * 1.609
end
3 Likes
#3

Velocity is in terms of studs per second.
1 stud is 20 meters.

1 meter per second is 2.237 miles per hour ( look it up or do the conversion math yourself if you dont believe me ).

Therefore to get mph you simply do
x * 20 * 2.237

For the sph multiply x by 60 twice.

Finally for kph, try it yourself, look up the conversion factor and just apply that knowledge

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#4 
local function toSPH(x)
	return x * 3600
end

local function toMPH(x)
	-- return (x / 1609.344 / 3.571 * 3600)
	return toSPH(x) / 3600
end

local function toKPH(x)
	--return x * (20000 / 3600)
	return toMPH(x) * 1.609
end

Alright so I did this. I used MPH and I multiplied by 1.609, as suggested by Google. However I think i did MPH wrong. Because in first one I multiply it by 3600 and then I divide it back by 3600.

2 Likes
#5

It depends on how many studs you want to consider to be part of a mile. That number would be multiplied by the result of SPH(x).

#6

So according to this post.

It appears to be: m = x/1609.344/3.571*3600, as the formula.

local function toSPH(x)
	return x * 3600
end

local function toMPH(x)
	return (x / 1609.344 / 3.571 * 3600)
	-- return toSPH(x) / 3600
end

local function toKPH(x)
	-- return x * (20000 / 3600)
	return toMPH(x) * 1.609
end

70 studs per second = 252000 studs per hour
70 studs per second = 43 miles per hour
70 studs per second = 70 kilometers per hour

1 Like
#7

Now that we have a conversion of studs to a real-life length unit we should use that and then convert kilometers to miles instead of the other way around.

local function toSPH(x)
	-- (x studs / second) * (3600 seconds / 1 hour) = (studs / second)
	return x * 3600
end

local function toKPH(x)
	-- (toSPH(x) studs / hour) * (1 m / 20 studs) * (1 km / 1000 m) = (km / hour)
	return toSPH(x) / 20000
end

local function toMPH(x)
	-- (toKPH(x) km / hour) * (0.6213 miles / 1 km) = (mi / hour)
	return toKPH(x) * .6213
end

This is the right one. The units are all correct.

1 Like
#8

Now it gives me 7 miles per hour for 70 studs per second and 12 kilometers per hour for 70 studs per second.

#9

My orginal formula for mph works. Although it might give higher numbers than you want, cause 1 stud being 20 meters would mean that 1 stud is pretty massive. You might want to play around with what you represent 1 stud to be, unless you just want it to be perfect.

#10

I will try your formula for miles per hour then.

#11

How come that 1 stud per second is 44 miles per hour.

local function toMPH(x)
	return x * 20 * 2.237
end
print(toMPH(1))

44.74
1 Like
How can I keep track of the Roblox Basic car's speed
#12

I just explained this to you. It is all relative to to what you represent 1 stud to be. Maybe you want 1 stud to be 2 meters, instead of 20. I just picked 20 cause it was on the wiki

#13

So according to Roblox Fandom Wiki. One stud is 0.28 meters.

#14

Then use 0.28, no one is stoping you. Its your game in the end of the day, make it what you believe best represents it.

#15
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#16

So 0.28 meters is 0.0001739839 miles.
That gives me 1 stud is equal to 0.0001739839 miles.
Does this mean that formula will be (studs * 3600) * 0.0001739839?

#17

Well there you go. Just play around with that number and find something you like. Try 1 stud being 2 meters.

1 Like
#18

And one stud is 0.00028 kilometers, given that 0.28 meters is 0.00028 kilometers.

#19

And by the way, despite having a decent understanding of imperial measures, I’m more used to metric measures instead.