At Digital Ocean you pay for the amount of storage your snapshot takes. This is prices at a simple $0.05 per gigabyte per month. This is different to Digital Ocean backups which are priced at 20% of the cost of the droplet no matter how much disk space you use. Backups are limited to once a week and only the last 4 weeks are retailed, where you can have as many snapshots as you wish.
Working Out Big A Snapshot Will Be.
If you want to know how much disk space your server is currently using so you can work out how much a snapshot will cost, you can run a simple command.
SSH into your server and run the df command
df -h /
root@server:~# df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 20G 8.3G 12G 43% /
Your command will output this table, you're looking for the /dev/vda1 drive which under the used column is tell me its using 8.3gb. 8.3*0.05=$0.415 per month storage costs.
We have also created a command for doing this all in one go and calculate the storage cost from terminal
df -k -h / | tail -1 | awk '{print $3*0.05}'
root@snapshooter:~# df -k -h / | tail -1 | awk '{print $3*0.05}'
0.415