diff --git a/src/components/input/NumericInputWithUnit.tsx b/src/components/input/NumericInputWithUnit.tsx
index 690fa2b..34077ee 100644
--- a/src/components/input/NumericInputWithUnit.tsx
+++ b/src/components/input/NumericInputWithUnit.tsx
@@ -1,16 +1,29 @@
 import React, { useState, useEffect } from 'react';
-import { Grid, TextField } from '@mui/material';
+import { Grid, TextField, Select, MenuItem } from '@mui/material';
 import TextFieldWithDesc from '@components/options/TextFieldWithDesc';
 import Autocomplete from '@mui/material/Autocomplete';
 import Qty from 'js-quantities';
-import { parse } from 'path';
-import { b } from 'vitest/dist/suite-IbNSsUWN.js';
+//
+
+const siPrefixes: { [key: string]: number } = {
+  '': 1,
+  k: 1000,
+  M: 1000000,
+  G: 1000000000,
+  T: 1000000000000,
+  m: 0.001,
+  u: 0.000001,
+  n: 0.000000001,
+  p: 0.000000000001
+};
 
 export default function NumericInputWithUnit(props: {
   value: { value: number; unit: string };
   onOwnChange: (value: { value: number; unit: string }, ...baseProps) => void;
+  defaultPrefix?: string;
 }) {
   const [inputValue, setInputValue] = useState(props.value.value);
+  const [prefix, setPrefix] = useState(props.defaultPrefix || '');
   const [unit, setUnit] = useState(props.value.unit);
   const [unitOptions, setUnitOptions] = useState<string[]>([]);
 
@@ -34,7 +47,7 @@ export default function NumericInputWithUnit(props: {
     setInputValue(newValue);
     if (props.onOwnChange) {
       try {
-        const qty = Qty(newValue, unit).to(val.unit);
+        const qty = Qty(newValue * siPrefixes[prefix], unit).to(val.unit);
         props.onOwnChange({ unit: val.unit, value: qty.scalar });
       } catch (error) {
         console.error('Conversion error', error);
@@ -42,11 +55,31 @@ export default function NumericInputWithUnit(props: {
     }
   };
 
+  const handlePrefixChange = (newPrefix: string) => {
+    const oldPrefixValue = siPrefixes[prefix];
+    const newPrefixValue = siPrefixes[newPrefix];
+
+    setPrefix(newPrefix);
+
+    // Value does not change, it is just re-formatted for display
+    // handleValueChange({
+    //   value: (inputValue * oldPrefixValue) / newPrefixValue,
+    //   unit: unit
+    // });
+  };
+
   const handleUnitChange = (newUnit: string) => {
     if (!newUnit) return;
+    const oldInputValue = inputValue;
+    const oldUnit = unit;
     setUnit(newUnit);
+    setPrefix('');
+
     try {
-      const convertedValue = Qty(inputValue, unit).to(newUnit).scalar;
+      const convertedValue = Qty(
+        oldInputValue * siPrefixes[prefix],
+        oldUnit
+      ).to(newUnit).scalar;
       setInputValue(convertedValue);
     } catch (error) {
       console.error('Unit conversion error', error);
@@ -63,20 +96,46 @@ export default function NumericInputWithUnit(props: {
   };
 
   return (
-    <Grid container spacing={2} alignItems="center">
+    <Grid
+      container
+      spacing={2}
+      alignItems="center"
+      style={{ minWidth: '20rem' }}
+    >
       <Grid item xs={6}>
         <TextFieldWithDesc
           {...props.baseProps}
           type="number"
           fullWidth
-          value={inputValue}
+          value={(inputValue / siPrefixes[prefix])
+            .toFixed(9)
+            .replace(/(\d*\.\d+?)0+$/, '$1')}
           onOwnChange={(value) =>
             handleValueChange({ value: parseFloat(value), unit: unit })
           }
           label="Value"
         />
       </Grid>
-      <Grid item xs={6}>
+
+      <Grid item xs={3}>
+        <Select
+          fullWidth
+          label="Prefix"
+          title="Prefix"
+          value={prefix}
+          onChange={(event, newValue) => {
+            handlePrefixChange(newValue.props.value || '');
+          }}
+        >
+          {Object.keys(siPrefixes).map((key) => (
+            <MenuItem key={key} value={key}>
+              {key}
+            </MenuItem>
+          ))}
+        </Select>
+      </Grid>
+
+      <Grid item xs={3}>
         <Autocomplete
           options={unitOptions}
           value={unit}
diff --git a/src/pages/tools/number/generic-calc/data/types.ts b/src/pages/tools/number/generic-calc/data/types.ts
index 52d6a57..3be9b75 100644
--- a/src/pages/tools/number/generic-calc/data/types.ts
+++ b/src/pages/tools/number/generic-calc/data/types.ts
@@ -7,6 +7,8 @@ export interface GenericCalcType {
     title: string;
     formula: string;
     unit: string;
+    // Si prefix default
+    defaultPrefix?: string;
   }[];
   selections?: {
     title: string;
@@ -20,7 +22,7 @@ export interface GenericCalcType {
     name: string;
     title: string;
     unit: string;
-
+    defaultPrefix?: string;
     // If absence, assume it's the default target var
     default?: number;
   }[];
diff --git a/src/pages/tools/number/generic-calc/data/wire_voltage_drop.ts b/src/pages/tools/number/generic-calc/data/wire_voltage_drop.ts
index 59deba8..fabe807 100644
--- a/src/pages/tools/number/generic-calc/data/wire_voltage_drop.ts
+++ b/src/pages/tools/number/generic-calc/data/wire_voltage_drop.ts
@@ -59,7 +59,8 @@ const voltagedropinwire: GenericCalcType = {
       name: 'p',
       title: 'Resistivity',
       unit: 'Ω/m3',
-      default: 1
+      default: 1,
+      defaultPrefix: 'n'
     },
     {
       name: 'x',
diff --git a/src/pages/tools/number/generic-calc/index.tsx b/src/pages/tools/number/generic-calc/index.tsx
index c1fe85b..707d04a 100644
--- a/src/pages/tools/number/generic-calc/index.tsx
+++ b/src/pages/tools/number/generic-calc/index.tsx
@@ -13,7 +13,6 @@ import React, { useState } from 'react';
 import ToolContent from '@components/ToolContent';
 import { ToolComponentProps } from '@tools/defineTool';
 import ToolTextResult from '@components/result/ToolTextResult';
-import TextFieldWithDesc from '@components/options/TextFieldWithDesc';
 import NumericInputWithUnit from '@components/input/NumericInputWithUnit';
 import { UpdateField } from '@components/options/ToolOptions';
 import { InitialValuesType } from './types';
@@ -51,7 +50,7 @@ export default async function makeTool(
     }>({});
 
     const [extraOutputs, setExtraOutputs] = useState<{
-      [key: string]: string;
+      [key: string]: number;
     }>({});
 
     const updateVarField = (
@@ -240,8 +239,8 @@ export default async function makeTool(
                       <TableCell>
                         <NumericInputWithUnit
                           title={variable.title}
-                          sx={{ width: '25ch' }}
                           description={valsBoundToPreset[variable.name] || ''}
+                          defaultPrefix={variable.defaultPrefix}
                           value={{
                             value:
                               values.outputVariable === variable.name
@@ -287,7 +286,17 @@ export default async function makeTool(
                   {calcData.extraOutputs?.map((extraOutput) => (
                     <TableRow key={extraOutput.title}>
                       <TableCell>{extraOutput.title}</TableCell>
-                      <TableCell>{extraOutputs[extraOutput.title]}</TableCell>
+                      <TableCell>
+                        <NumericInputWithUnit
+                          title={extraOutput.title}
+                          disabled={true}
+                          defaultPrefix={extraOutput.defaultPrefix}
+                          value={{
+                            value: extraOutputs[extraOutput.title],
+                            unit: extraOutput.unit
+                          }}
+                        ></NumericInputWithUnit>
+                      </TableCell>
                       <TableCell>{extraOutput.unit}</TableCell>
                       <TableCell></TableCell>
                     </TableRow>
@@ -345,7 +354,9 @@ export default async function makeTool(
               const result: nerdamer.Expression = expr.evaluate();
 
               if (result) {
-                extraOutputs[extraOutput.title] = result.toDecimal();
+                extraOutputs[extraOutput.title] = parseFloat(
+                  result.toDecimal()
+                );
               }
             }
           }