diff --git a/app/imports/api/creature/computation/afterComputation/evaluateString.js b/app/imports/api/creature/computation/afterComputation/evaluateString.js
index 9753d963..e012ff58 100644
--- a/app/imports/api/creature/computation/afterComputation/evaluateString.js
+++ b/app/imports/api/creature/computation/afterComputation/evaluateString.js
@@ -18,7 +18,12 @@ export default function evaluateString(string, scope, fn = 'compile'){
     errors.push(e);
     return {result: string, errors};
   }
-
+  // Parsing failed
+  if (node === null){
+    errors.push('...');
+    return {result: string, errors};
+  }
+  console.log(node);
   let context = new CompilationContext();
   let result = node[fn](scope, context);
   if (result instanceof ConstantNode){
diff --git a/app/imports/api/creature/computation/engine/ComputationMemo.js b/app/imports/api/creature/computation/engine/ComputationMemo.js
index 8bf93765..4fd412a3 100644
--- a/app/imports/api/creature/computation/engine/ComputationMemo.js
+++ b/app/imports/api/creature/computation/engine/ComputationMemo.js
@@ -6,6 +6,7 @@ import findAncestorByType from '/imports/api/creature/computation/engine/findAnc
 export default class ComputationMemo {
   constructor(props, creature){
     this.statsByVariableName = {};
+    this.constantsByVariableName = {};
     this.extraStatsByVariableName = {};
     this.statsById = {};
     this.originalPropsById = {};
@@ -51,13 +52,15 @@ export default class ComputationMemo {
         return true;
       }
     }).forEach((prop) => {
-      // Now add all effects and proficiencies
+      // Now add everything else
       if (prop.type === 'effect'){
         this.addEffect(prop);
       } else if (prop.type === 'proficiency') {
         this.addProficiency(prop);
       } else if (prop.type === 'classLevel'){
         this.addClassLevel(prop);
+      } else if (prop.type === 'constant'){
+        this.addConstant(prop);
       } else {
         this.addEndStepProp(prop);
       }
@@ -72,6 +75,14 @@ export default class ComputationMemo {
       }
     }
   }
+  addConstant(prop){
+    prop = this.registerProperty(prop);
+    if (
+      !this.constantsByVariableName[prop.variableName]
+    ){
+      this.constantsByVariableName[prop.variableName] = prop
+    }
+  }
   registerProperty(prop){
     this.originalPropsById[prop._id] = cloneDeep(prop);
     this.propsById[prop._id] = prop;
diff --git a/app/imports/api/creature/computation/engine/evaluateCalculation.js b/app/imports/api/creature/computation/engine/evaluateCalculation.js
index fb49431c..de972e6a 100644
--- a/app/imports/api/creature/computation/engine/evaluateCalculation.js
+++ b/app/imports/api/creature/computation/engine/evaluateCalculation.js
@@ -42,11 +42,75 @@ export default function evaluateCalculation({
       dependencies,
     };
   }
+
+  // Replace constants with their parsed constant
+  let failed = replaceConstants({calc, memo, prop, dependencies, errors})
+  if (failed){
+    return {
+      context: {errors},
+      result: new ConstantNode({value: string, type: 'string'}),
+      dependencies,
+    };
+  }
+
   // Ensure all symbol nodes are defined and computed
+  computeSymbols({calc, memo, prop, dependencies})
+
+  // Evaluate
+  let context = new CompilationContext();
+  let result = calc[fn](memo.statsByVariableName, context);
+  return {result, context, dependencies};
+}
+
+// Replace constants in the calc with the right ParseNodes
+function replaceConstants({calc, memo, prop, dependencies, errors}){
+  let constFailed = [];
+  calc.replaceNodes(node => {
+    if (!(node instanceof SymbolNode)) return;
+    let stat, constant;
+    if (node.name[0] !== '#'){
+      stat = memo.statsByVariableName[node.name]
+      constant = memo.constantsByVariableName[node.name];
+    } else if (node.name === '#constant'){
+      constant = findAncestorByType({type: 'constant', prop, memo});
+    }
+    // replace constants that aren't overridden by stats
+    if (constant && !stat){
+      dependencies = union(dependencies, [
+        constant._id,
+        ...constant.dependencies
+      ]);
+      // Fail if the constant has errors
+      if (constant.errors && constant.errors.length){
+        constFailed.push(node.name);
+        return;
+      }
+      let parsedConstantNode;
+      try {
+        parsedConstantNode = parse(constant.calculation);
+      } catch(e){
+        constFailed.push(node.name);
+        return;
+      }
+      if (!parsedConstantNode) constFailed.push(node.name);
+      return parsedConstantNode;
+    }
+  });
+  constFailed.forEach(name => {
+    errors.push({
+      type: 'error',
+      message: `${name} is a constant property with parsing errors`
+    });
+  });
+  return !!constFailed.length;
+}
+
+  // Ensure all symbol nodes are defined and computed
+function computeSymbols({calc, memo, prop, dependencies}){
   calc.traverse(node => {
     if (node instanceof SymbolNode || node instanceof AccessorNode){
-      // References up the tree start with $
       let stat;
+      // References up the tree start with #
       if (node.name[0] === '#'){
         stat = findAncestorByType({type: node.name.slice(1), prop, memo});
         memo.statsByVariableName[node.name] = stat;
@@ -64,8 +128,4 @@ export default function evaluateCalculation({
       }
     }
   });
-  // Evaluate
-  let context = new CompilationContext();
-  let result = calc[fn](memo.statsByVariableName, context);
-  return {result, context, dependencies};
 }
diff --git a/app/imports/api/properties/Constants.js b/app/imports/api/properties/Constants.js
index 3a805547..830ee526 100644
--- a/app/imports/api/properties/Constants.js
+++ b/app/imports/api/properties/Constants.js
@@ -1,6 +1,9 @@
 import SimpleSchema from 'simpl-schema';
 import VARIABLE_NAME_REGEX from '/imports/constants/VARIABLE_NAME_REGEX.js';
-
+import ErrorSchema from '/imports/api/properties/subSchemas/ErrorSchema.js';
+import { parse, CompilationContext } from '/imports/parser/parser.js';
+import AccessorNode from '/imports/parser/parseTree/AccessorNode.js';
+import SymbolNode from '/imports/parser/parseTree/SymbolNode.js';
 /*
  * Constants are primitive values that can be used elsewhere in computations
  */
@@ -22,14 +25,59 @@ let ConstantSchema = new SimpleSchema({
 		type: String,
 		optional: true,
 	},
-  // The value, or array of values
-  result: {
-    type: SimpleSchema.oneOf(String, Number, Boolean, Array),
-    maxSize: 32,
+  errors: {
+    type: Array,
+    autoValue(){
+      let calc = this.field('calculation');
+      if (!calc.isSet && this.isModifier) {
+        this.unset()
+        return;
+      }
+      let string = calc.value;
+      // Evaluate the calculation with no scope
+      let {result, errors} = parseString(string);
+      // Any errors will result in a failure
+      if (errors.length) return errors;
+      // Ban variables in constants if necessary
+      result && result.traverse(node => {
+        if (node instanceof SymbolNode || node instanceof AccessorNode){
+          errors.push({
+            type: 'error',
+            message: 'Variables can\'t be used to define a constant'
+          });
+        }
+      });
+      return errors;
+    }
+  },
+  'errors.$':{
+    type: ErrorSchema,
   },
-  'result.$': {
-    type: SimpleSchema.oneOf(String, Number, Boolean),
-  }
 });
 
+function parseString(string, fn = 'compile'){
+  let errors = [];
+  if (!string){
+    return {result: string, errors};
+  }
+
+  // Parse the string using mathjs
+  let node;
+  try {
+    node = parse(string);
+  } catch (e) {
+    let message = e.toString().split('.')[0];
+    errors.push({type: 'error', message});
+    return {result: string, errors};
+  }
+  // Parsing incomplete
+  if (node === null){
+    errors.push({type: 'warning', message: 'Unexpected end of input'});
+    return {result: string, errors};
+  }
+  let context = new CompilationContext();
+  let result = node[fn]({/*empty scope*/}, context);
+  return {result, errors: context.errors}
+}
+
 export { ConstantSchema };
diff --git a/app/imports/api/properties/computedPropertySchemasIndex.js b/app/imports/api/properties/computedPropertySchemasIndex.js
index 273ae54f..5bb0e9d0 100644
--- a/app/imports/api/properties/computedPropertySchemasIndex.js
+++ b/app/imports/api/properties/computedPropertySchemasIndex.js
@@ -5,6 +5,7 @@ import { ComputedAttackSchema } from '/imports/api/properties/Attacks.js';
 import { ComputedAttributeSchema } from '/imports/api/properties/Attributes.js';
 import { ComputedBuffSchema } from '/imports/api/properties/Buffs.js';
 import { ClassLevelSchema } from '/imports/api/properties/ClassLevels.js';
+import { ConstantSchema } from '/imports/api/properties/Constants.js';
 import { ComputedContainerSchema } from '/imports/api/properties/Containers.js';
 import { ComputedDamageSchema } from '/imports/api/properties/Damages.js';
 import { DamageMultiplierSchema } from '/imports/api/properties/DamageMultipliers.js';
@@ -30,6 +31,7 @@ const propertySchemasIndex = {
   attribute: ComputedAttributeSchema,
   buff: ComputedBuffSchema,
   classLevel: ClassLevelSchema,
+  constant: ConstantSchema,
   damage: ComputedDamageSchema,
   damageMultiplier: DamageMultiplierSchema,
   effect: ComputedEffectSchema,
diff --git a/app/imports/api/properties/propertySchemasIndex.js b/app/imports/api/properties/propertySchemasIndex.js
index cc88f2ba..9a3596ab 100644
--- a/app/imports/api/properties/propertySchemasIndex.js
+++ b/app/imports/api/properties/propertySchemasIndex.js
@@ -5,6 +5,7 @@ import { AttackSchema } from '/imports/api/properties/Attacks.js';
 import { AttributeSchema } from '/imports/api/properties/Attributes.js';
 import { BuffSchema } from '/imports/api/properties/Buffs.js';
 import { ClassLevelSchema } from '/imports/api/properties/ClassLevels.js';
+import { ConstantSchema } from '/imports/api/properties/Constants.js';
 import { DamageSchema } from '/imports/api/properties/Damages.js';
 import { DamageMultiplierSchema } from '/imports/api/properties/DamageMultipliers.js';
 import { EffectSchema } from '/imports/api/properties/Effects.js';
@@ -30,6 +31,7 @@ const propertySchemasIndex = {
   attribute: AttributeSchema,
   buff: BuffSchema,
   classLevel: ClassLevelSchema,
+  constant: ConstantSchema,
   damage: DamageSchema,
   damageMultiplier: DamageMultiplierSchema,
   effect: EffectSchema,
diff --git a/app/imports/constants/PROPERTIES.js b/app/imports/constants/PROPERTIES.js
index 18646ac7..ab8e5b0b 100644
--- a/app/imports/constants/PROPERTIES.js
+++ b/app/imports/constants/PROPERTIES.js
@@ -23,6 +23,10 @@ const PROPERTIES = Object.freeze({
     icon: '$vuetify.icons.class_level',
     name: 'Class level'
   },
+  constant: {
+    icon: 'anchor',
+    name: 'Constant'
+  },
   container: {
     icon: 'work',
     name: 'Container'
diff --git a/app/imports/parser/parseTree/ArrayNode.js b/app/imports/parser/parseTree/ArrayNode.js
index 62e0bbd7..2f31fa69 100644
--- a/app/imports/parser/parseTree/ArrayNode.js
+++ b/app/imports/parser/parseTree/ArrayNode.js
@@ -33,4 +33,7 @@ export default class ArrayNode extends ParseNode {
     fn(this);
     this.values.forEach(value => value.traverse(fn));
   }
+  replaceChildren(fn){
+    this.values = this.values.map(node => node.replaceNodes(fn));
+  }
 }
diff --git a/app/imports/parser/parseTree/CallNode.js b/app/imports/parser/parseTree/CallNode.js
index a603c6aa..12cab9e4 100644
--- a/app/imports/parser/parseTree/CallNode.js
+++ b/app/imports/parser/parseTree/CallNode.js
@@ -54,6 +54,9 @@ export default class CallNode extends ParseNode {
     fn(this);
     this.args.forEach(arg => arg.traverse(fn));
   }
+  replaceChildren(fn){
+    this.args = this.args.map(arg => arg.replaceNodes(fn));
+  }
 }
 
 function castArgsToType({fn, scope, context, args, type}){
diff --git a/app/imports/parser/parseTree/IfNode.js b/app/imports/parser/parseTree/IfNode.js
index 8ffe7831..a94f21c2 100644
--- a/app/imports/parser/parseTree/IfNode.js
+++ b/app/imports/parser/parseTree/IfNode.js
@@ -34,4 +34,9 @@ export default class IfNode extends ParseNode {
     this.consequent.traverse(fn);
     this.alternative.traverse(fn);
   }
+  replaceChildren(fn){
+    this.condition = this.condition.replaceNodes(fn);
+    this.consequent = this.consequent.replaceNodes(fn);
+    this.alternative = this.alternative.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/IndexNode.js b/app/imports/parser/parseTree/IndexNode.js
index 8f7684f2..850ff088 100644
--- a/app/imports/parser/parseTree/IndexNode.js
+++ b/app/imports/parser/parseTree/IndexNode.js
@@ -29,4 +29,8 @@ export default class IndexNode extends ParseNode {
     this.array.traverse(fn);
     this.index.traverse(fn);
   }
+  replaceChildren(fn){
+    this.array = this.array.replaceNodes(fn);
+    this.index = this.index.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/NotOperatorNode.js b/app/imports/parser/parseTree/NotOperatorNode.js
index 64568f59..47aca511 100644
--- a/app/imports/parser/parseTree/NotOperatorNode.js
+++ b/app/imports/parser/parseTree/NotOperatorNode.js
@@ -28,4 +28,7 @@ export default class NotOperatorNode extends ParseNode {
     fn(this);
     this.right.traverse(fn);
   }
+  replaceChildren(fn){
+    this.right = this.right.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/OperatorNode.js b/app/imports/parser/parseTree/OperatorNode.js
index 6fe63428..7bd546de 100644
--- a/app/imports/parser/parseTree/OperatorNode.js
+++ b/app/imports/parser/parseTree/OperatorNode.js
@@ -60,4 +60,8 @@ export default class OperatorNode extends ParseNode {
     this.left.traverse(fn);
     this.right.traverse(fn);
   }
+  replaceChildren(fn){
+    this.left = this.left.replaceNodes(fn);
+    this.right = this.right.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/ParenthesisNode.js b/app/imports/parser/parseTree/ParenthesisNode.js
index abe600b3..eda6038f 100644
--- a/app/imports/parser/parseTree/ParenthesisNode.js
+++ b/app/imports/parser/parseTree/ParenthesisNode.js
@@ -23,4 +23,7 @@ export default class ParenthesisNode extends ParseNode {
     fn(this);
     this.content.traverse(fn);
   }
+  replaceChildren(fn){
+    this.content = this.content.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/ParseNode.js b/app/imports/parser/parseTree/ParseNode.js
index 2379081a..740c7b14 100644
--- a/app/imports/parser/parseTree/ParseNode.js
+++ b/app/imports/parser/parseTree/ParseNode.js
@@ -30,4 +30,14 @@ export default class ParseNode {
   traverse(fn){
     fn(this);
   }
+  // replace nodes, only replace nodes if fn returns a value
+  replaceNodes(fn){
+    let newNode = fn(this);
+    if (newNode) {
+      return newNode;
+    } else {
+      if (this.replaceChildren) this.replaceChildren(fn)
+      return this;
+    }
+  }
 }
diff --git a/app/imports/parser/parseTree/RollNode.js b/app/imports/parser/parseTree/RollNode.js
index d44bff4c..be84e690 100644
--- a/app/imports/parser/parseTree/RollNode.js
+++ b/app/imports/parser/parseTree/RollNode.js
@@ -64,4 +64,8 @@ export default class RollNode extends ParseNode {
     this.left.traverse(fn);
     this.right.traverse(fn);
   }
+  replaceChildren(fn){
+    this.left = this.left.replaceNodes(fn);
+    this.right = this.right.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/parser/parseTree/UnaryOperatorNode.js b/app/imports/parser/parseTree/UnaryOperatorNode.js
index 3f53014c..c8109e6a 100644
--- a/app/imports/parser/parseTree/UnaryOperatorNode.js
+++ b/app/imports/parser/parseTree/UnaryOperatorNode.js
@@ -34,4 +34,7 @@ export default class UnaryOperatorNode extends ParseNode {
     fn(this);
     this.right.traverse(fn);
   }
+  replaceChildren(fn){
+    this.right = this.right.replaceNodes(fn);
+  }
 }
diff --git a/app/imports/ui/properties/forms/ConstantForm.vue b/app/imports/ui/properties/forms/ConstantForm.vue
new file mode 100644
index 00000000..ef4fd46b
--- /dev/null
+++ b/app/imports/ui/properties/forms/ConstantForm.vue
@@ -0,0 +1,51 @@
+<template lang="html">
+  <div>
+    <div class="layout row wrap">
+      <text-field
+        label="Name"
+        :value="model.name"
+        :error-messages="errors.name"
+        @change="change('name', ...arguments)"
+      />
+      <text-field
+        label="Variable name"
+        :value="model.variableName"
+        style="flex-basis: 300px;"
+        hint="Use this name in formulae to reference this attribute"
+        :error-messages="errors.variableName"
+        @change="change('variableName', ...arguments)"
+      />
+    </div>
+    <text-field
+      label="Value"
+      :value="model.calculation"
+      :error-messages="errors.calculation"
+      @change="change('calculation', ...arguments)"
+    />
+    <calculation-error-list :errors="clientErrors" />
+  </div>
+</template>
+
+<script>
+import propertyFormMixin from '/imports/ui/properties/forms/shared/propertyFormMixin.js';
+import CalculationErrorList from '/imports/ui/properties/forms/shared/CalculationErrorList.vue';
+import { ConstantSchema } from '/imports/api/properties/Constants.js';
+
+export default {
+  components: {
+    CalculationErrorList,
+  },
+  mixins: [propertyFormMixin],
+  computed: {
+    // We can't rely on autoValue running in every form, so recalculate errors
+    clientErrors(){
+      let validationContext = ConstantSchema.newContext();
+      let cleanModel = validationContext.clean(this.model);
+      return cleanModel.errors;
+    }
+  }
+}
+</script>
+
+<style lang="css" scoped>
+</style>
diff --git a/app/imports/ui/properties/forms/shared/CalculationErrorList.vue b/app/imports/ui/properties/forms/shared/CalculationErrorList.vue
index 11ba5090..63b649ca 100644
--- a/app/imports/ui/properties/forms/shared/CalculationErrorList.vue
+++ b/app/imports/ui/properties/forms/shared/CalculationErrorList.vue
@@ -15,7 +15,7 @@
         :color="errorColor(error.type)"
         outline
       >
-        {{ error.message }}
+        <pre>{{ error.message }}</pre>
       </v-alert>
     </v-slide-x-transition>
   </div>
diff --git a/app/imports/ui/properties/forms/shared/propertyFormIndex.js b/app/imports/ui/properties/forms/shared/propertyFormIndex.js
index 360733a1..7f2c9a8c 100644
--- a/app/imports/ui/properties/forms/shared/propertyFormIndex.js
+++ b/app/imports/ui/properties/forms/shared/propertyFormIndex.js
@@ -4,6 +4,7 @@ import AttackForm from '/imports/ui/properties/forms/AttackForm.vue';
 import AttributeForm from '/imports/ui/properties/forms/AttributeForm.vue';
 import BuffForm from '/imports/ui/properties/forms/BuffForm.vue';
 import ClassLevelForm from '/imports/ui/properties/forms/ClassLevelForm.vue';
+import ConstantForm from '/imports/ui/properties/forms/ConstantForm.vue';
 import ContainerForm from '/imports/ui/properties/forms/ContainerForm.vue';
 import DamageForm from '/imports/ui/properties/forms/DamageForm.vue';
 import DamageMultiplierForm from '/imports/ui/properties/forms/DamageMultiplierForm.vue';
@@ -28,6 +29,7 @@ export default {
   attack: AttackForm,
   attribute: AttributeForm,
   buff: BuffForm,
+  constant: ConstantForm,
   container: ContainerForm,
   classLevel: ClassLevelForm,
   damage: DamageForm,
diff --git a/app/imports/ui/utility/evaluate.js b/app/imports/ui/utility/evaluate.js
deleted file mode 100644
index f93c3a85..00000000
--- a/app/imports/ui/utility/evaluate.js
+++ /dev/null
@@ -1,38 +0,0 @@
-import Creatures from '/imports/api/creature/Creatures.js';
-
-// Computations resolve to numbers
-// vars is a dict of variables to substitute
-export function evaluateComputation(string, vars){
-  console.warn('Deprecated, evaluate computation should be done by the computation engine')
-  if (!string) return string;
-  // Replace all the string variables with numbers if possible
-  let substitutedString = string.replace(
-    /\w*[a-z]\w*/gi,
-    sub => vars.hasOwnProperty(sub) ? vars[sub] : sub
-  );
-
-  // Evaluate the expression to a number or return it as is.
-  try {
-    return math.eval(substitutedString);
-  } catch (e){
-    return substitutedString;
-  }
-}
-
-// Strings can have computations in bracers like so: {computation}
-// vars is a dict of variables to substitute
-export function evaluateStringWithVariables(string, vars){
-  console.warn('Deprecated, evaluateStringWithVariables should be done by the computation engine')
-	if (!string) return string;
-  // Compute everything inside bracers
-	return string.replace(/\{([^\{\}]*)\}/g, function(match, p1){
-		return evaluateComputation(p1, vars);
-	});
-}
-
-export function evaluateStringForCharId(string, charId){
-  console.warn('Deprecated, evaluateStringForCharId should be done by the computation engine')
-  let char = Creatures.findOne(charId, {fields: {variables: 1}});
-  let vars = char ? char.variables : {};
-  return evaluateStringWithVariables(string, vars);
-}