Build
Choose heroes and monsters, configure their supported options, and place both sides on a tactical map.
Tactical simulator
Preparing tactical map…
A tactical D&D 5.5e combat simulator
Encounterra resolves complete 2024 fifth-edition combats instead of stopping at an XP estimate. Configure the combatants and battlefield, run Monte Carlo simulations, and examine how the encounter actually unfolds.
From setup to replay
How Encounterra works
Simulate
Run repeated battles in which combatants move, choose targets, use resources, and respond to changing conditions.
Inspect and replay
Compare outcomes and combatant performance, read complete logs, and replay individual battles on the map.
Supported tactical depth
What Encounterra simulates
Smarter decisions throughout every turn
Combatants consider where to move, who to target, what to spend, and what could happen next before they act.
Complete attacks and abilities
Combatants use the full options available on their stat blocks.
Teamwork and reactions
Combatants use their abilities at useful moments and help the allies who benefit most.
Build the encounter you want
Adjust supported heroes, monsters, and their starting conditions.
Battlefields that matter
Position, visibility, and terrain can all change the outcome.
Generate a balanced opposing team
Build a Low, Moderate, or High opponent roster from the selected heroes using the 2024 encounter XP budgets.
Encounter Chaining
Send the same party through several fights and see how well they survive the full journey.
Common questions
D&D 5.5e combat simulator FAQ
Is Encounterra free?
Yes. Encounterra is a free, browser-based D&D 5.5e combat simulator. You can build and run an encounter without installing software.
Which D&D rules does Encounterra use?
Encounterra is built around the 2024 revision of fifth edition and System Reference Document 5.2.1. It simulates the rules, creatures, character options, and abilities currently implemented; it does not replace the full tabletop rules or a DM’s rulings.
How is Encounterra different from an encounter difficulty calculator?
An XP calculator estimates difficulty from encounter budgets. Encounterra repeatedly resolves the combat itself, including movement, targeting, attacks, supported spells and abilities, resource use, and changing battlefield conditions.
Does the battlefield affect a simulation?
Yes. Starting positions, movement, range, visibility, difficult terrain, obstacles, lighting, hazards, flight, burrowing, and other supported tactical conditions can change how a battle plays out.
What results can I inspect?
Encounterra reports victory and casualty rates, round counts, and combatant performance. Completed simulations can also provide detailed logs and animated replays of individual battles.
Can Encounterra simulate several encounters in sequence?
Yes. Encounter chains carry hit points and spent resources between battles, with optional short rests between selected encounters.