When we asked the moving companies, they gave us very different estimates. Eventually, I have decided to do by myself. I did a Google spreadsheet where I have listed all our items and added some formulas to calculate the number of things, their volume and size.
I feel that I need to share this masterpiece with you. Because our office located in Europe, all the units are in European format. Still, I think so you can easily modify the spreadsheet to do it in US units.
Below is the link to the file, We have closed it by the social locker, so you need to like our Facebook page or Twitter. I believe you'll find it fair since it will make you more comfortable.
Please comment if you have any suggestions or have a better version!