You'd be surprised how many times I've been told that I'm not. Even as we are talking to people about why we celebrate Easter; this question/concern has come out time and time again.
When I was younger, probably 8 or 9, I was finished playing at a friends house and my mom came to pick me up. When I got in the car and shut the door I told my mom about a conversation I had with my friend. This is, to an effect, my conversation with my mom:
me: so-and-so asked if we were christian and I told her no.
mom: (laughing) why did you say no?
me: because, I told her we're mormon!
mom: do you belive in Jesus Christ?
mom: do you follow what He teaches?
mom: (still laughing) then you're christian!
So if I didn't know I was a christian for the first 8 or 9 years of my life, I can't expect you to know either. Many other christian denominations feel we aren't to be considered christian because of our doctrinal differences. However our claim is we are christian. The only reason we differ doctrinally is because of further modern-day revelation from God. However, this revelation does not dispute nor change the fact that Christ is still our Savior. We follow Him, we are saved by Him, and we are trying to become more like Him always.
One of my favorite hymns we sing at church is titled: "Come Follow Me". In the first verse we sing:
"Come follow me", the Savior said
then let us in His footsteps tread
for this alone can we be one
With God's own, loved begotten son.
An apostle of the Lord said: "following Christ is not a casual or occasional practice, but a continuous commitment and way of life that applies at all times and in all places."(Followers of Christ, Dallin H. Oaks, April 2013) We do not put anyone or anything above our Savior, Jesus Christ and our Heavenly Father who sent Him. And we try to live our lives in such a way that displays that devotion to Him.
If you're still not sure that mormons are christian, find a mormon near you and observe their actions. Are they following "in His footsteps tread?" Are they trying to make His teachings a way of life? We aren't perfect--oh no, no, no; but we understand to some small degree where happiness comes from and "to what source [we] may look for a remission of [our] sins" (2 Nephi 25:26, Book of Mormon)
So now you know...pass it on :)
With much love,
link to quoted talk: https://www.lds.org/general-conference/2013/04/followers-of-christ?lang=eng