diff --git a/README.md b/README.md
index ff2d5e7..5bf9ae2 100644
--- a/README.md
+++ b/README.md
@@ -36,13 +36,13 @@ const valueWithVariable = runArithmetic('2 * four', {
 console.log(valueWithVariable); // 8
 ```
 
-### `getOperands(formulaText: string): string[]`
+### `getVariables(formulaText: string): string[]`
 
 Usage example:
 
 ```js
-import { getOperands } from '@beyondessential/arithmetic';
+import { getVariables } from '@beyondessential/arithmetic';
 
-const operands = getOperands('(-a * b) / 3');
-console.log(operands); // ['a', 'b', '3']
+const variables = getVariables('(-a * b - 1) / (c + 3)');
+console.log(variables); // ['a', 'b', 'c']
 ```
diff --git a/__tests__/symbols.test.js b/__tests__/symbols.test.js
index bfc6233..6189278 100644
--- a/__tests__/symbols.test.js
+++ b/__tests__/symbols.test.js
@@ -5,22 +5,22 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import { getOperands } from '../src/symbols';
+import { getVariables } from '../src/symbols';
 
-describe('getOperands()', () => {
+describe('getVariables()', () => {
   const testData = [
-    ['numbers', '1 + 2', ['1', '2']],
     ['single letters', 'a + b', ['a', 'b']],
     ['words', 'alpha + beta', ['alpha', 'beta']],
+    ['formula includes numbers', '2 * a + b - 1', ['a', 'b']],
     ["'u' letter", 'a + u', ['a', 'u']],
     ["words containing 'u', 'x'", 'user * experience - ux', ['user', 'experience', 'ux']],
     ['excessive whitespace', ' a  +  b ', ['a', 'b']],
     ['no whitespace', 'a+b', ['a', 'b']],
-    ['same operand multiple times', 'a * b + a', ['a', 'b']],
-    ['all operators', '(a + -b) / ((2 * c) - 3 x d)', ['a', 'b', '2', 'c', '3', 'd']],
+    ['same variable multiple times', 'a * b + a', ['a', 'b']],
+    ['all operators', '(a + -b) / ((2 * c) - 3 x d)', ['a', 'b', 'c', 'd']],
   ];
 
   it.each(testData)('%s', (_, formula, expected) => {
-    expect(getOperands(formula)).toStrictEqual(expected);
+    expect(getVariables(formula)).toStrictEqual(expected);
   });
 });
diff --git a/index.d.ts b/index.d.ts
index 49541a7..9b455ca 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-export function getOperands(formulaText: string): string[];
+export function getVariables(formulaText: string): string[];
 export function runArithmetic(
   formulaText: string,
   values?: Record<string, string | number>,
diff --git a/package.json b/package.json
index fdf8755..9bb8cb2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@beyondessential/arithmetic",
-  "version": "1.0.0",
+  "version": "2.0.0",
   "description": "Utility to evaluate BODMAS arithmetic formulas",
   "keywords": [
     "arithmetic",
diff --git a/src/index.js b/src/index.js
index d3e5fca..c01399e 100644
--- a/src/index.js
+++ b/src/index.js
@@ -6,4 +6,4 @@
  */
 
 export { runArithmetic } from './arithmetic';
-export { getOperands } from './symbols';
+export { getVariables } from './symbols';
diff --git a/src/symbols.js b/src/symbols.js
index db9204a..d2b79b5 100644
--- a/src/symbols.js
+++ b/src/symbols.js
@@ -25,12 +25,12 @@ export function getPrecedence(operator) {
   }
 }
 
-export function getOperands(formulaText) {
-  const operands = formulaText
+export function getVariables(formulaText) {
+  const variables = formulaText
     // Replace the alternate multiplication symbol 'x' with a non-alphanumeric character
     .replace(/(^|\W)x(\W|$)/, ' ')
     .split(/[+-/*() ]/g)
-    .filter(c => c !== '');
+    .filter(v => v !== '' && Number.isNaN(Number(v)));
 
-  return [...new Set(operands)];
+  return [...new Set(variables)];
 }