The following is a list of online tools I use that help save time preparing encounters for D&D. I’m not going to go into details about each one though I may refer to some of them in my blog posts. I urge you to check them out.
Last updated: August 15, 2017.
Monster Maker. A downloadable application for creating professional-looking stat blocks.
Online Die Roller. Useful for rolling PC stats or calculating median hit points for a monster.
5e Random Encounter Generator. Create random encounters based on terrain type.
CR Calculator. Plug in adjusted monster stats and calculate CR. A knowledge of how to do it manually is required for this to be accurate as you have to make adjustments for abilities on your own, but this saves a lot of time.
Tome of Knowedge. Mobile reference tool with stat blocks, spells, and conditions. Allows changes on-the-fly to monster hit dice and AC. Excellent reference to use at the table.
Kobold Fight Club. This is one of the most popular DM tools on the internet. It has CR information for monsters from just about any source you can think of from third-party books to the official ones from WotC. It allows you to predict the challenge of a group of monsters.
Fantasy Name Generators. The must robust name generator I’ve found. It is regularly updated and has generators for all the 5e races as well as races from earlier editions. It also has generators for other tabletop and video games.
Customizeable Fantasy Name Generator. This name generator allows you to set your own rules for name conventions and then generate names based on them. It does take some work to get it going, but it’s good if you want to generate names for a homebrew campaign or for an obscure race or culture in D&D lore.
Job Titles. While not an RPG resource, this site contains the names of early jobs that you would find in a fantasy setting that may or may not exist any longer in modern culture. Some examples are anchorite, jobmaster, and tanner. Particularly useful for NPCs and creation of towns and cities.
D&D Map-a-week Archive. This is an archive of maps that WotC posted on their website between 2000 and 2007. Although it is no longer updated it is a treasure-trove of maps, including some iconic locations.
Redkat’s 5e Tools. This site has a few different tools for DMs. My favorites are the random treasure generator and the spellbook generator.
Forgotten Realms Wiki. You probably already know about this one if you run a Forgotten Realms campaign, but it’s worth mentioning. It contains a lot of info from decades of lore though it is still lacking in 5e timeline info. I recommend using this in conjunction with the Sword Coast Adventurer’s Guide if you run a Forgotten Realms campaign.
Adventure Lookup. As seen on Matthew Colville’s YouTube channel. Need an adventure in swamp ruins? Need an adventure with a vampire spawn villain? This brand new resource allows you to search an ever expanding database of published adventures that you can run or drop into a campaign as a side quest.
Homebrewery. This one is rather popular, especially with DMs who make their content available on DM’s Guild. It allows you to make your homebrew look like official 5e offerings. It takes a little bit of playing around to learn, but is totally worth it.
RPG Cards. I use this tool to print out cards for my players for magic items. I find the 3×5″ size to be optimal and I laminate them for longevity (I also do this with maps that will be used more than 1-2 sessions). The picture below shows what they look like. I print mine in grayscale because I use a B&W laser printer, but this tool allows you to print in color, as well as print double-sided cards.