# Conversion Formula **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2005, 7:48pm UTC](https://boards.straightdope.com/t/conversion-formula/313024 "2005-07-18T19:48:58Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![pointaken](https://avatars.discourse-cdn.com/v4/letter/p/3be4f8/32.png) [@pointaken](https://boards.straightdope.com/u/pointaken)\ **Post date:** [July 18, 2005, 7:48pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/1 "2005-07-18T19:48:58Z")
Is there a mathematical conversion for volume to weight? Specifically for liters to pounds? ---
**Author:** ![micco](https://avatars.discourse-cdn.com/v4/letter/m/5f8ce5/32.png) [@micco](https://boards.straightdope.com/u/micco)\ **Post date:** [July 18, 2005, 8:01pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/2 "2005-07-18T20:01:56Z")
What you need is density, which is mass per unit volume, for the material you’re interested in. A liter of air and a liter of water would have much different mass (and therefore weight) because they have different densities. ---
**Author:** ![DMC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dmc/32/18049_2.png) [@DMC](https://boards.straightdope.com/u/DMC)\ **Post date:** [July 18, 2005, 8:02pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/3 "2005-07-18T20:02:35Z")
Of what substance? ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [July 18, 2005, 8:03pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/4 "2005-07-18T20:03:16Z")
Not all liquids have the same weight /volume ratio. ---
**Author:** ![sciguy](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@sciguy](https://boards.straightdope.com/u/sciguy)\ **Post date:** [July 18, 2005, 8:16pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/5 "2005-07-18T20:16:22Z")
> [@pointaken](#): > > Is there a mathematical conversion for volume to weight? Specifically for liters to pounds? Weight = volume \* density You’ll probably need some conversion factors to get the weight to come out in the right units depending on the volume and density units you have to work with. For example, for water (density approx 1 g / mL or 1 kg / L): Weight (pounds) = N liters \* ( 1 kg / L ) \* ( 2.205 pounds / kg ) Weight (pounds) = N \* 2.205 Other materials have different densities, but the general procedure would be the same with different numbers. Just keep the units on all values to make sure stuff cancels out properly. And before I get jumped on, I’m well aware that mass does not equal weight, but I figure the OP is doing his/her work on Earth, so I played a little fast-and-loose with terminology. ---
**Author:** ![pointaken](https://avatars.discourse-cdn.com/v4/letter/p/3be4f8/32.png) [@pointaken](https://boards.straightdope.com/u/pointaken)\ **Post date:** [July 18, 2005, 8:31pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/6 "2005-07-18T20:31:24Z")
If the conversion is one to one for water, why would I double it to 2.205? The liquid I am using is a slimfast type product. Would you still suggest the 2.205 measurement? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [July 18, 2005, 8:35pm UTC](https://boards.straightdope.com/t/conversion-formula/313024/7 "2005-07-18T20:35:32Z")
The conversion for water is 1:1 in the metric system, because that’s the way the metric system was designed. To convert kilograms to pounds you must multiply by 2.205