diff --git a/src/theme/calc/CSSCalculator.ts b/src/theme/calc/CSSCalculator.ts
index 7c25fcc..77c2e9a 100644
--- a/src/theme/calc/CSSCalculator.ts
+++ b/src/theme/calc/CSSCalculator.ts
@@ -1,15 +1,16 @@
+import { isNumber } from '../../util';
 import AbstractCalculator from './calculator';
 
 const CALC_UNIT = 'CALC_UNIT';
 
 const regexp = new RegExp(CALC_UNIT, 'g');
 
-function unit(value: string | number) {
-  if (typeof value === 'number') {
+const unit = (value: string | number) => {
+  if (isNumber(value)) {
     return `${value}${CALC_UNIT}`;
   }
   return value;
-}
+};
 
 export default class CSSCalculator extends AbstractCalculator {
   result: string = '';
@@ -30,8 +31,8 @@ export default class CSSCalculator extends AbstractCalculator {
 
     if (num instanceof CSSCalculator) {
       this.result = `(${num.result})`;
-    } else if (numType === 'number') {
-      this.result = unit(num as number);
+    } else if (isNumber(num)) {
+      this.result = unit(num);
     } else if (numType === 'string') {
       this.result = num as string;
     }
diff --git a/src/util/index.ts b/src/util/index.ts
index 648135a..5741803 100644
--- a/src/util/index.ts
+++ b/src/util/index.ts
@@ -155,12 +155,16 @@ export function supportLogicProps(): boolean {
 
 export const isClientSide = canUseDom();
 
-export function unit(num: string | number) {
-  if (typeof num === 'number') {
+export const isNumber = (val: any): val is number => {
+  return typeof val === 'number' && !Number.isNaN(val);
+};
+
+export const unit = (num: string | number) => {
+  if (isNumber(num)) {
     return `${num}px`;
   }
   return num;
-}
+};
 
 export function toStyleStr(
   style: string,