diff --git a/src/main/angular/src/app/editor/siPrefix.ts b/src/main/angular/src/app/editor/siPrefix.ts
index aabff20..2f06f16 100644
--- a/src/main/angular/src/app/editor/siPrefix.ts
+++ b/src/main/angular/src/app/editor/siPrefix.ts
@@ -1,4 +1,4 @@
-export const SI_PREFIXES: string[] = ['f', 'p', 'n', 'µ', 'm', '', 'k', 'M', 'G', 'T', 'E', 'P'];
+export const SI_PREFIXES: string[] = ['q', 'r', 'y', 'z', 'a', 'f', 'p', 'n', 'µ', 'm', '', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y', 'R', 'Q'];
 
 export function siPrefix(value: number, unit: string, minDigits: number): string {
   if (value === 0) {
@@ -7,8 +7,8 @@ export function siPrefix(value: number, unit: string, minDigits: number): string
   const negative = value < 0;
   value = negative ? -value : value;
   const exp0 = Math.log10(value);
-  const group = Math.floor(exp0 / 3);
-  const index = group + 5;
+  const group = Math.max(-10, Math.min(+10, Math.floor(exp0 / 3)));
+  const index = group + 10;
   const prefix = SI_PREFIXES[index];
   const exp1 = group * 3;
   const factor = Math.pow(10, -exp1);