diff --git a/package.json b/package.json
index 024dd0ad..b53d93db 100644
--- a/package.json
+++ b/package.json
@@ -24,6 +24,7 @@
     "@solid-primitives/set": "^0.4.3",
     "eventemitter3": "^5.0.0",
     "isomorphic-ws": "^5.0.0",
+    "long": "^5.2.1",
     "revolt-api": "^0.5.17",
     "solid-js": "^1.7.2",
     "ulid": "^2.3.0",
diff --git a/src/classes/Channel.ts b/src/classes/Channel.ts
index 60a0314d..8bb69448 100644
--- a/src/classes/Channel.ts
+++ b/src/classes/Channel.ts
@@ -2,9 +2,11 @@ import { ReactiveMap } from "@solid-primitives/map";
 import type { Channel as ApiChannel } from "revolt-api";
 import { decodeTime } from "ulid";
 
-import { Client, FileArgs } from "../Client";
+import { Client } from "../Client";
 import { hydrate } from "../hydration";
 import { HydratedChannel } from "../hydration/channel";
+import { bitwiseAndEq, calculatePermission } from "../permissions/calculator";
+import { Permission } from "../permissions/definitions";
 import { ObjectStorage } from "../storage/ObjectStorage";
 
 export default (client: Client) =>
@@ -164,6 +166,13 @@ export default (client: Client) =>
       return Channel.#storage.get(this.id).active;
     }
 
+    /**
+     * User Ids of recipients of the group
+     */
+    get recipientIds() {
+      return Channel.#storage.get(this.id).recipientIds;
+    }
+
     /**
      * Recipients of the group
      */
@@ -313,4 +322,23 @@ export default (client: Client) =>
         true
       );
     }
+
+    /**
+     * Permission the currently authenticated user has against this channel
+     */
+    get permission() {
+      return calculatePermission(client, this);
+    }
+
+    /**
+     * Check whether we have a given permission in a channel
+     * @param permission Permission Names
+     * @returns Whether we have this permission
+     */
+    havePermission(...permission: (keyof typeof Permission)[]) {
+      return bitwiseAndEq(
+        this.permission,
+        ...permission.map((x) => Permission[x])
+      );
+    }
   };
diff --git a/src/classes/Server.ts b/src/classes/Server.ts
index 0180708a..4de4e948 100644
--- a/src/classes/Server.ts
+++ b/src/classes/Server.ts
@@ -4,6 +4,8 @@ import { decodeTime } from "ulid";
 
 import { Channel, Client } from "../Client";
 import { HydratedServer } from "../hydration/server";
+import { bitwiseAndEq, calculatePermission } from "../permissions/calculator";
+import { Permission } from "../permissions/definitions";
 import { ObjectStorage } from "../storage/ObjectStorage";
 
 export default (client: Client) =>
@@ -113,6 +115,13 @@ export default (client: Client) =>
       return new Date(decodeTime(this.id));
     }
 
+    /**
+     * Owner's user ID
+     */
+    get ownerId() {
+      return Server.#storage.get(this.id).ownerId;
+    }
+
     /**
      * Owner
      */
@@ -322,4 +331,33 @@ export default (client: Client) =>
         max_side: 256,
       });
     }
+
+    /**
+     * Own member object for this server
+     */
+    get member() {
+      return client.serverMembers.get({
+        server: this.id,
+        user: client.user!.id,
+      });
+    }
+
+    /**
+     * Permission the currently authenticated user has against this server
+     */
+    get permission() {
+      return calculatePermission(client, this);
+    }
+
+    /**
+     * Check whether we have a given permission in a server
+     * @param permission Permission Names
+     * @returns Whether we have this permission
+     */
+    havePermission(...permission: (keyof typeof Permission)[]) {
+      return bitwiseAndEq(
+        this.permission,
+        ...permission.map((x) => Permission[x])
+      );
+    }
   };
diff --git a/src/classes/ServerMember.ts b/src/classes/ServerMember.ts
index 8526bfb2..f3c7a765 100644
--- a/src/classes/ServerMember.ts
+++ b/src/classes/ServerMember.ts
@@ -1,8 +1,10 @@
 import { ReactiveMap } from "@solid-primitives/map";
 import type { Member as ApiMember, MemberCompositeKey } from "revolt-api";
 
-import { Client } from "../Client";
+import { Channel, Client, Server } from "../Client";
 import { HydratedServerMember } from "../hydration/serverMember";
+import { bitwiseAndEq, calculatePermission } from "../permissions/calculator";
+import { Permission } from "../permissions/definitions";
 import { ObjectStorage } from "../storage/ObjectStorage";
 
 /**
@@ -173,4 +175,94 @@ export default (client: Client) =>
     get timeout() {
       return ServerMember.#storage.get(key(this.id)).timeout;
     }
+
+    /**
+     * Ordered list of roles for this member, from lowest to highest priority.
+     */
+    get orderedRoles() {
+      const server = this.server!;
+      return (
+        this.roles
+          ?.map((id) => ({
+            id,
+            ...server.roles?.get(id),
+          }))
+          .sort((a, b) => b.rank! - a.rank!) ?? []
+      );
+    }
+
+    /**
+     * Member's currently hoisted role.
+     */
+    get hoistedRole() {
+      const roles = this.orderedRoles.filter((x) => x.hoist);
+      if (roles.length > 0) {
+        return roles[roles.length - 1];
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Member's current role colour.
+     */
+    get roleColour() {
+      const roles = this.orderedRoles.filter((x) => x.colour);
+      if (roles.length > 0) {
+        return roles[roles.length - 1].colour;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Member's ranking.
+     * Smaller values are ranked as higher priotity.
+     */
+    get ranking() {
+      if (this.id.user === this.server?.ownerId) {
+        return -Infinity;
+      }
+
+      const roles = this.orderedRoles;
+      if (roles.length > 0) {
+        return roles[roles.length - 1].rank!;
+      } else {
+        return Infinity;
+      }
+    }
+
+    /**
+     * Get the permissions that this member has against a certain object
+     * @param target Target object to check permissions against
+     * @returns Permissions that this member has
+     */
+    getPermissions(target: Server | Channel) {
+      return calculatePermission(client, target, { member: this });
+    }
+
+    /**
+     * Check whether a member has a certain permission against a certain object
+     * @param target Target object to check permissions against
+     * @param permission Permission names to check for
+     * @returns Whether the member has this permission
+     */
+    hasPermission(
+      target: Server | Channel,
+      ...permission: (keyof typeof Permission)[]
+    ) {
+      return bitwiseAndEq(
+        this.getPermissions(target),
+        ...permission.map((x) => Permission[x])
+      );
+    }
+
+    /**
+     * Checks whether the target member has a higher rank than this member.
+     * @param target The member to compare against
+     * @returns Whether this member is inferior to the target
+     */
+    inferiorTo(target: ServerMember) {
+      return target.ranking < this.ranking;
+    }
   };
diff --git a/src/classes/User.ts b/src/classes/User.ts
index 16607fbf..4f2dcd34 100644
--- a/src/classes/User.ts
+++ b/src/classes/User.ts
@@ -4,6 +4,7 @@ import { decodeTime } from "ulid";
 
 import { Client, FileArgs } from "../Client";
 import { HydratedUser } from "../hydration/user";
+import { U32_MAX, UserPermission } from "../permissions/definitions";
 import { ObjectStorage } from "../storage/ObjectStorage";
 
 export default (client: Client) =>
@@ -207,4 +208,43 @@ export default (client: Client) =>
         client.generateFileURL(this.avatar, ...args) ?? this.defaultAvatarURL
       );
     }
+
+    /**
+     * Permissions against this user
+     */
+    get permission() {
+      let permissions = 0;
+      switch (this.relationship) {
+        case "Friend":
+        case "User":
+          return U32_MAX;
+        case "Blocked":
+        case "BlockedOther":
+          return UserPermission.Access;
+        case "Incoming":
+        case "Outgoing":
+          permissions = UserPermission.Access;
+      }
+
+      if (
+        client.channels
+          .toList()
+          .find(
+            (channel) =>
+              (channel.type === "Group" || channel.type === "DirectMessage") &&
+              channel.recipientIds?.includes(client.user!.id)
+          ) ||
+        client.serverMembers
+          .toList()
+          .find((member) => member.id.user === client.user!.id)
+      ) {
+        if (client.user?.bot || this.bot) {
+          permissions |= UserPermission.SendMessage;
+        }
+
+        permissions |= UserPermission.Access | UserPermission.ViewProfile;
+      }
+
+      return permissions;
+    }
   };
diff --git a/src/permissions/calculator.ts b/src/permissions/calculator.ts
new file mode 100644
index 00000000..aca6e6ac
--- /dev/null
+++ b/src/permissions/calculator.ts
@@ -0,0 +1,160 @@
+import Long from "long";
+
+import { Channel, Client, Server, ServerMember } from "..";
+
+import {
+  ALLOW_IN_TIMEOUT,
+  DEFAULT_PERMISSION_DIRECT_MESSAGE,
+  DEFAULT_PERMISSION_VIEW_ONLY,
+  Permission,
+  UserPermission,
+} from "./definitions";
+
+/**
+ * Check whether `b` is present in `a`
+ * @param a Input A
+ * @param b Inputs (OR'd together)
+ */
+export function bitwiseAndEq(a: number, ...b: number[]) {
+  const value = b.reduce((prev, cur) => prev.or(cur), Long.fromNumber(0));
+  return value.and(a).eq(value);
+}
+
+/**
+ * Calculate permissions against a given object
+ * @param target Target object to check permissions against
+ * @param options Additional options to use when calculating
+ */
+export function calculatePermission(
+  client: Client,
+  target: Channel | Server,
+  options?: {
+    /**
+     * Pretend to be another ServerMember
+     */
+    member?: ServerMember;
+  }
+): number {
+  const user = options?.member ? options?.member.user : client.user;
+  if (user?.privileged) {
+    return Permission.GrantAllSafe;
+  }
+
+  if (target instanceof client.servers) {
+    // 1. Check if owner.
+    if (target.owner === user?.id) {
+      return Permission.GrantAllSafe;
+    } else {
+      // 2. Get ServerMember.
+      const member = options?.member ??
+        client.serverMembers.get({
+          user: user!.id,
+          server: target.id,
+        }) ?? { roles: null, timeout: null };
+
+      if (!member) return 0;
+
+      // 3. Apply allows from default_permissions.
+      let perm = Long.fromNumber(target.defaultPermissions);
+
+      // 4. If user has roles, iterate in order.
+      if (member.roles && target.roles) {
+        // 5. Apply allows and denies from roles.
+        const permissions = member.orderedRoles.map(
+          (role) => role.permissions ?? { a: 0, d: 0 }
+        );
+
+        for (const permission of permissions) {
+          perm = perm.or(permission.a).and(Long.fromNumber(permission.d).not());
+        }
+      }
+
+      // 5. Revoke permissions if ServerMember is timed out.
+      if (member.timeout && member.timeout > new Date()) {
+        perm = perm.and(ALLOW_IN_TIMEOUT);
+      }
+
+      return perm.toNumber();
+    }
+  } else {
+    // 1. Check channel type.
+    switch (target.type) {
+      case "SavedMessages":
+        return Permission.GrantAllSafe;
+      case "DirectMessage": {
+        // 2. Determine user permissions.
+        const user_permissions = target.recipient?.permission || 0;
+
+        // 3. Check if the user can send messages.
+        if (user_permissions & UserPermission.SendMessage) {
+          return DEFAULT_PERMISSION_DIRECT_MESSAGE;
+        } else {
+          return DEFAULT_PERMISSION_VIEW_ONLY;
+        }
+      }
+      case "Group": {
+        // 2. Check if user is owner.
+        if (target.ownerId === user!.id) {
+          return DEFAULT_PERMISSION_DIRECT_MESSAGE;
+        } else {
+          // 3. Pull out group permissions.
+          return target.permissions ?? DEFAULT_PERMISSION_DIRECT_MESSAGE;
+        }
+      }
+      case "TextChannel":
+      case "VoiceChannel": {
+        // 2. Get server.
+        const server = target.server;
+        if (typeof server === "undefined") return 0;
+
+        // 3. If server owner, just grant all permissions.
+        if (server.owner === user?.id) {
+          return Permission.GrantAllSafe;
+        } else {
+          // 4. Get ServerMember.
+          const member = options?.member ??
+            client.serverMembers.get({
+              user: user!.id,
+              server: server.id,
+            }) ?? { roles: null, timeout: null };
+
+          if (!member) return 0;
+
+          // 5. Calculate server base permissions.
+          let perm = Long.fromNumber(
+            calculatePermission(client, server, options)
+          );
+
+          // 6. Apply default allows and denies for channel.
+          if (target.defaultPermissions) {
+            perm = perm
+              .or(target.defaultPermissions.a)
+              .and(Long.fromNumber(target.defaultPermissions.d).not());
+          }
+
+          // 7. If user has roles, iterate in order.
+          if (member.roles && target.rolePermissions && server.roles) {
+            // 5. Apply allows and denies from roles.
+            const roles = member.orderedRoles.map(({ id }) => id);
+
+            for (const id of roles) {
+              const override = target.rolePermissions[id];
+              if (override) {
+                perm = perm
+                  .or(override.a)
+                  .and(Long.fromNumber(override.d).not());
+              }
+            }
+          }
+
+          // 8. Revoke permissions if ServerMember is timed out.
+          if (member.timeout && member.timeout > new Date()) {
+            perm = perm.and(ALLOW_IN_TIMEOUT);
+          }
+
+          return perm.toNumber();
+        }
+      }
+    }
+  }
+}
diff --git a/src/permissions/definitions.ts b/src/permissions/definitions.ts
new file mode 100644
index 00000000..f711adf3
--- /dev/null
+++ b/src/permissions/definitions.ts
@@ -0,0 +1,141 @@
+/**
+ * Permission against User
+ */
+export const UserPermission = {
+  Access: 1 << 0,
+  ViewProfile: 1 << 1,
+  SendMessage: 1 << 2,
+  Invite: 1 << 3,
+};
+
+/**
+ * Permission against Server / Channel
+ */
+export const Permission = {
+  // * Generic permissions
+  /// Manage the channel or channels on the server
+  ManageChannel: 2 ** 0,
+  /// Manage the server
+  ManageServer: 2 ** 1,
+  /// Manage permissions on servers or channels
+  ManagePermissions: 2 ** 2,
+  /// Manage roles on server
+  ManageRole: 2 ** 3,
+  /// Manage server customisation (includes emoji)
+  ManageCustomisation: 2 ** 4,
+
+  // % 1 bits reserved
+
+  // * Member permissions
+  /// Kick other members below their ranking
+  KickMembers: 2 ** 6,
+  /// Ban other members below their ranking
+  BanMembers: 2 ** 7,
+  /// Timeout other members below their ranking
+  TimeoutMembers: 2 ** 8,
+  /// Assign roles to members below their ranking
+  AssignRoles: 2 ** 9,
+  /// Change own nickname
+  ChangeNickname: 2 ** 10,
+  /// Change or remove other's nicknames below their ranking
+  ManageNicknames: 2 ** 11,
+  /// Change own avatar
+  ChangeAvatar: 2 ** 12,
+  /// Remove other's avatars below their ranking
+  RemoveAvatars: 2 ** 13,
+
+  // % 7 bits reserved
+
+  // * Channel permissions
+  /// View a channel
+  ViewChannel: 2 ** 20,
+  /// Read a channel's past message history
+  ReadMessageHistory: 2 ** 21,
+  /// Send a message in a channel
+  SendMessage: 2 ** 22,
+  /// Delete messages in a channel
+  ManageMessages: 2 ** 23,
+  /// Manage webhook entries on a channel
+  ManageWebhooks: 2 ** 24,
+  /// Create invites to this channel
+  InviteOthers: 2 ** 25,
+  /// Send embedded content in this channel
+  SendEmbeds: 2 ** 26,
+  /// Send attachments and media in this channel
+  UploadFiles: 2 ** 27,
+  /// Masquerade messages using custom nickname and avatar
+  Masquerade: 2 ** 28,
+  /// React to messages with emoji
+  React: 2 ** 29,
+
+  // * Voice permissions
+  /// Connect to a voice channel
+  Connect: 2 ** 30,
+  /// Speak in a voice call
+  Speak: 2 ** 31,
+  /// Share video in a voice call
+  Video: 2 ** 32,
+  /// Mute other members with lower ranking in a voice call
+  MuteMembers: 2 ** 33,
+  /// Deafen other members with lower ranking in a voice call
+  DeafenMembers: 2 ** 34,
+  /// Move members between voice channels
+  MoveMembers: 2 ** 35,
+
+  // * Misc. permissions
+  // % Bits 36 to 52: free area
+  // % Bits 53 to 64: do not use
+
+  // * Grant all permissions
+  /// Safely grant all permissions
+  GrantAllSafe: 0x000f_ffff_ffff_ffff,
+};
+
+/**
+ * Maximum safe value
+ */
+export const U32_MAX = 2 ** 32 - 1; // 4294967295
+
+/**
+ * Permissions allowed for a user while in timeout
+ */
+export const ALLOW_IN_TIMEOUT =
+  Permission.ViewChannel + Permission.ReadMessageHistory;
+
+/**
+ * Default permissions if we can only view
+ */
+export const DEFAULT_PERMISSION_VIEW_ONLY =
+  Permission.ViewChannel + Permission.ReadMessageHistory;
+
+/**
+ * Default base permissions for channels
+ */
+export const DEFAULT_PERMISSION =
+  DEFAULT_PERMISSION_VIEW_ONLY +
+  Permission.SendMessage +
+  Permission.InviteOthers +
+  Permission.SendEmbeds +
+  Permission.UploadFiles +
+  Permission.Connect +
+  Permission.Speak;
+
+/**
+ * Permissions in saved messages channel
+ */
+export const DEFAULT_PERMISSION_SAVED_MESSAGES = Permission.GrantAllSafe;
+
+/**
+ * Permissions in direct message channels / default permissions for group DMs
+ */
+export const DEFAULT_PERMISSION_DIRECT_MESSAGE =
+  DEFAULT_PERMISSION + Permission.React + Permission.ManageChannel;
+
+/**
+ * Permissions in server text / voice channel
+ */
+export const DEFAULT_PERMISSION_SERVER =
+  DEFAULT_PERMISSION +
+  Permission.React +
+  Permission.ChangeNickname +
+  Permission.ChangeAvatar;