diff --git a/packages/ui-utils/src/formatters.ts b/packages/ui-utils/src/formatters.ts
index 76869c9..f55309a 100644
--- a/packages/ui-utils/src/formatters.ts
+++ b/packages/ui-utils/src/formatters.ts
@@ -1,23 +1,23 @@
-export function formatBytes(bytes: number): string {
+export function formatBytes(bytes: number, precision = 2): string {
   if (bytes === 0) return '0 B';
   const units = ['B', 'KB', 'MB', 'GB'];
   const i = Math.floor(Math.log2(bytes) / 10);
-  return `${(bytes / (1 << (i * 10))).toFixed(2)} ${units[i]}`;
+  return `${(bytes / (1 << (i * 10))).toFixed(precision)} ${units[i]}`;
 }
 
-export function formatNumber(num: number): string {
-  if (num >= 1e9) return (num / 1e9).toFixed(2) + 'B';
-  if (num >= 1e6) return (num / 1e6).toFixed(2) + 'M';
-  if (num >= 1e3) return (num / 1e3).toFixed(2) + 'K';
+export function formatNumber(num: number, precision = 2): string {
+  if (num >= 1e9) return (num / 1e9).toFixed(precision) + 'B';
+  if (num >= 1e6) return (num / 1e6).toFixed(precision) + 'M';
+  if (num >= 1e3) return (num / 1e3).toFixed(precision) + 'K';
   return num.toString();
 }
 
-export function formatTime(seconds: number): string {
-  if (seconds < 0.001) return (seconds * 1e6).toFixed(2) + 'μs';
-  if (seconds < 1) return (seconds * 1000).toFixed(2) + 'ms';
+export function formatTime(seconds: number, precision = 2): string {
+  if (seconds < 0.001) return (seconds * 1e6).toFixed(precision) + 'μs';
+  if (seconds < 1) return (seconds * 1000).toFixed(precision) + 'ms';
   return seconds.toFixed(3) + 's';
 }
 
-export function formatPercent(value: number): string {
-  return (value * 100).toFixed(2) + '%';
+export function formatPercent(value: number, precision = 2): string {
+  return (value * 100).toFixed(precision) + '%';
 }
diff --git a/packages/web/src/components/Analysis.tsx b/packages/web/src/components/Analysis.tsx
index 2fc65ca..14c29ac 100644
--- a/packages/web/src/components/Analysis.tsx
+++ b/packages/web/src/components/Analysis.tsx
@@ -46,7 +46,8 @@ const TOOLTIPS = {
   attrSelect: 'Number of attribute selections performed (accessing .attr from an attribute set)',
 };
 
-const Analysis: Component<{ stats: StatsData }> = props => {
+const Analysis: Component<{ stats: StatsData; precision?: number }> = props => {
+  const prec = () => props.precision ?? 2;
   const totalMemory = createMemo(
     () =>
       props.stats.envs.bytes +
@@ -105,18 +106,22 @@ const Analysis: Component<{ stats: StatsData }> = props => {
         <div class="header-stats">
           <MetricCard
             label="CPU Time"
-            value={formatTime(props.stats.cpuTime)}
+            value={formatTime(props.stats.cpuTime, prec())}
             tooltip={TOOLTIPS.cpuTime}
           />
-          <MetricCard label="Memory" value={formatBytes(totalMemory())} tooltip={TOOLTIPS.memory} />
+          <MetricCard
+            label="Memory"
+            value={formatBytes(totalMemory(), prec())}
+            tooltip={TOOLTIPS.memory}
+          />
           <MetricCard
             label="Expressions"
-            value={formatNumber(props.stats.nrExprs)}
+            value={formatNumber(props.stats.nrExprs, prec())}
             tooltip={TOOLTIPS.nrExprs}
           />
           <MetricCard
             label="Thunks"
-            value={`${formatNumber(props.stats.nrAvoided)} / ${formatNumber(props.stats.nrThunks)}`}
+            value={`${formatNumber(props.stats.nrAvoided, prec())} / ${formatNumber(props.stats.nrThunks, prec())}`}
             tooltip="Avoided / Created thunks. Avoided means the value was already computed and reused."
             highlight={props.stats.nrAvoided >= props.stats.nrThunks}
           />
@@ -131,11 +136,11 @@ const Analysis: Component<{ stats: StatsData }> = props => {
               <div class="gc-header">GC Statistics</div>
               <div class="gc-values">
                 <span class="gc-label">Heap:</span>
-                <span class="gc-value">{formatBytes(props.stats.gc?.heapSize || 0)}</span>
+                <span class="gc-value">{formatBytes(props.stats.gc?.heapSize || 0, prec())}</span>
                 <span class="gc-label">Allocated:</span>
-                <span class="gc-value">{formatBytes(props.stats.gc?.totalBytes || 0)}</span>
+                <span class="gc-value">{formatBytes(props.stats.gc?.totalBytes || 0, prec())}</span>
                 <span class="gc-label">Cycles:</span>
-                <span class="gc-value">{formatNumber(props.stats.gc?.cycles || 0)}</span>
+                <span class="gc-value">{formatNumber(props.stats.gc?.cycles || 0, prec())}</span>
               </div>
             </div>
           </Show>
@@ -143,15 +148,15 @@ const Analysis: Component<{ stats: StatsData }> = props => {
 
         <Section title="Time & Thunks" collapsible>
           <div class="time-thunks-combined">
-            <TimeChart stats={props.stats} />
+            <TimeChart stats={props.stats} precision={prec()} />
             <div class="thunks-section">
-              <ThunkChart stats={props.stats} />
+              <ThunkChart stats={props.stats} precision={prec()} />
             </div>
           </div>
         </Section>
 
         <Section title="Operations" collapsible>
-          <OperationsChart stats={props.stats} />
+          <OperationsChart stats={props.stats} precision={prec()} />
         </Section>
       </div>
 
@@ -160,17 +165,17 @@ const Analysis: Component<{ stats: StatsData }> = props => {
           <div class="metrics-grid small">
             <MetricCard
               label="Count"
-              value={formatNumber(props.stats.envs.number)}
+              value={formatNumber(props.stats.envs.number, prec())}
               tooltip={TOOLTIPS.envsNumber}
             />
             <MetricCard
               label="Elements"
-              value={formatNumber(props.stats.envs.elements)}
+              value={formatNumber(props.stats.envs.elements, prec())}
               tooltip={TOOLTIPS.envsElements}
             />
             <MetricCard
               label="Memory"
-              value={formatBytes(props.stats.envs.bytes)}
+              value={formatBytes(props.stats.envs.bytes, prec())}
               tooltip={TOOLTIPS.envsBytes}
             />
           </div>
@@ -180,22 +185,22 @@ const Analysis: Component<{ stats: StatsData }> = props => {
           <div class="metrics-grid small">
             <MetricCard
               label="Values"
-              value={formatNumber(props.stats.values.number)}
+              value={formatNumber(props.stats.values.number, prec())}
               tooltip={TOOLTIPS.valuesNumber}
             />
             <MetricCard
               label="Value Bytes"
-              value={formatBytes(props.stats.values.bytes)}
+              value={formatBytes(props.stats.values.bytes, prec())}
               tooltip={TOOLTIPS.valuesBytes}
             />
             <MetricCard
               label="Symbols"
-              value={formatNumber(props.stats.symbols.number)}
+              value={formatNumber(props.stats.symbols.number, prec())}
               tooltip={TOOLTIPS.symbolsNumber}
             />
             <MetricCard
               label="Symbol Bytes"
-              value={formatBytes(props.stats.symbols.bytes)}
+              value={formatBytes(props.stats.symbols.bytes, prec())}
               tooltip={TOOLTIPS.symbolsBytes}
             />
           </div>
@@ -205,22 +210,22 @@ const Analysis: Component<{ stats: StatsData }> = props => {
           <div class="metrics-grid small">
             <MetricCard
               label="List Elements"
-              value={formatNumber(props.stats.list.elements)}
+              value={formatNumber(props.stats.list.elements, prec())}
               tooltip={TOOLTIPS.listElements}
             />
             <MetricCard
               label="Concat Ops"
-              value={formatNumber(props.stats.list.concats)}
+              value={formatNumber(props.stats.list.concats, prec())}
               tooltip={TOOLTIPS.listConcats}
             />
             <MetricCard
               label="Set Count"
-              value={formatNumber(props.stats.sets.number)}
+              value={formatNumber(props.stats.sets.number, prec())}
               tooltip={TOOLTIPS.setsNumber}
             />
             <MetricCard
               label="Attributes"
-              value={formatNumber(props.stats.sets.elements)}
+              value={formatNumber(props.stats.sets.elements, prec())}
               tooltip={TOOLTIPS.setsElements}
             />
           </div>
@@ -235,7 +240,7 @@ const Analysis: Component<{ stats: StatsData }> = props => {
                 <div class="top-item">
                   <span class="rank">{i() + 1}</span>
                   <span class="name">{item.name}</span>
-                  <span class="count">{formatNumber(item.count)}</span>
+                  <span class="count">{formatNumber(item.count, prec())}</span>
                 </div>
               )}
             </For>
@@ -251,7 +256,7 @@ const Analysis: Component<{ stats: StatsData }> = props => {
                 <div class="top-item">
                   <span class="rank">{i() + 1}</span>
                   <span class="name">{item.name || '<lambda>'}</span>
-                  <span class="count">{formatNumber(item.count)}</span>
+                  <span class="count">{formatNumber(item.count, prec())}</span>
                   <span class="location">
                     {item.file}:{item.line}
                   </span>
@@ -267,22 +272,22 @@ const Analysis: Component<{ stats: StatsData }> = props => {
           <div class="metrics-grid small">
             <MetricCard
               label="NAR Reads"
-              value={formatNumber(props.stats.narRead || 0)}
+              value={formatNumber(props.stats.narRead || 0, prec())}
               tooltip={TOOLTIPS.narRead}
             />
             <MetricCard
               label="NAR Writes"
-              value={formatNumber(props.stats.narWrite || 0)}
+              value={formatNumber(props.stats.narWrite || 0, prec())}
               tooltip={TOOLTIPS.narWrite}
             />
             <MetricCard
               label="Read Bytes"
-              value={formatBytes(props.stats.narReadBytes || 0)}
+              value={formatBytes(props.stats.narReadBytes || 0, prec())}
               tooltip={TOOLTIPS.narReadBytes}
             />
             <MetricCard
               label="Write Bytes"
-              value={formatBytes(props.stats.narWriteBytes || 0)}
+              value={formatBytes(props.stats.narWriteBytes || 0, prec())}
               tooltip={TOOLTIPS.narWriteBytes}
             />
           </div>
@@ -299,7 +304,7 @@ const Analysis: Component<{ stats: StatsData }> = props => {
                   <span class="location">
                     {item.file}:{item.line}
                   </span>
-                  <span class="count">{formatNumber(item.count)}</span>
+                  <span class="count">{formatNumber(item.count, prec())}</span>
                 </div>
               )}
             </For>
diff --git a/packages/web/src/components/ComparisonView.tsx b/packages/web/src/components/ComparisonView.tsx
index c989099..1c7941e 100644
--- a/packages/web/src/components/ComparisonView.tsx
+++ b/packages/web/src/components/ComparisonView.tsx
@@ -10,9 +10,11 @@ interface ComparisonViewProps {
   entries: ComparisonEntry[];
   onSelect: (entry: ComparisonEntry) => void;
   onDelete: (id: number) => void;
+  precision?: number;
 }
 
 const ComparisonView: Component<ComparisonViewProps> = props => {
+  const prec = () => props.precision ?? 2;
   const [leftEntry, setLeftEntry] = createSignal<ComparisonEntry | null>(null);
   const [rightEntry, setRightEntry] = createSignal<ComparisonEntry | null>(null);
 
@@ -203,7 +205,7 @@ const ComparisonView: Component<ComparisonViewProps> = props => {
                           <Show when={!row.isReduction}>
                             <ArrowUpIcon size={14} />
                           </Show>
-                          {Math.abs(row.change).toFixed(2)}%
+                          {Math.abs(row.change).toFixed(prec())}%
                         </span>
                       </Show>
                     }
diff --git a/packages/web/src/components/OperationsChart.tsx b/packages/web/src/components/OperationsChart.tsx
index 13c28e2..d49fa35 100644
--- a/packages/web/src/components/OperationsChart.tsx
+++ b/packages/web/src/components/OperationsChart.tsx
@@ -4,9 +4,11 @@ import { formatNumber } from '@ns/ui-utils';
 
 interface OperationsChartProps {
   stats: StatsData;
+  precision?: number;
 }
 
 const OperationsChart: Component<OperationsChartProps> = props => {
+  const prec = () => props.precision ?? 2;
   const operations = createMemo(() =>
     [
       { label: 'Lookups', value: props.stats.nrLookups, colorClass: 'chart-1' },
@@ -34,7 +36,7 @@ const OperationsChart: Component<OperationsChartProps> = props => {
                 }}
               />
             </div>
-            <div class="op-value">{formatNumber(item.value)}</div>
+            <div class="op-value">{formatNumber(item.value, prec())}</div>
           </div>
         )}
       </For>
diff --git a/packages/web/src/components/ThunkChart.tsx b/packages/web/src/components/ThunkChart.tsx
index e403ad8..7a78938 100644
--- a/packages/web/src/components/ThunkChart.tsx
+++ b/packages/web/src/components/ThunkChart.tsx
@@ -4,9 +4,11 @@ import { formatNumber } from '@ns/ui-utils';
 
 interface ThunkChartProps {
   stats: StatsData;
+  precision?: number;
 }
 
 const ThunkChart: Component<ThunkChartProps> = props => {
+  const prec = () => props.precision ?? 2;
   const maxValue = createMemo(() => Math.max(props.stats.nrThunks, props.stats.nrAvoided));
 
   const avoidedRatio = createMemo(() => {
@@ -47,7 +49,7 @@ const ThunkChart: Component<ThunkChartProps> = props => {
         <div class="ratio-bar">
           <div class="ratio-fill" style={{ width: `${avoidedRatio() * 100}%` }} />
         </div>
-        <span class="ratio-label">Avoidance rate: {(avoidedRatio() * 100).toFixed(1)}%</span>
+        <span class="ratio-label">Avoidance rate: {(avoidedRatio() * 100).toFixed(prec())}%</span>
       </div>
     </div>
   );
diff --git a/packages/web/src/components/TimeChart.tsx b/packages/web/src/components/TimeChart.tsx
index 50b07bc..2f5737b 100644
--- a/packages/web/src/components/TimeChart.tsx
+++ b/packages/web/src/components/TimeChart.tsx
@@ -4,9 +4,11 @@ import { formatBytes, formatTime, formatPercent } from '@ns/ui-utils';
 
 interface TimeChartProps {
   stats: StatsData;
+  precision?: number;
 }
 
 const TimeChart: Component<TimeChartProps> = props => {
+  const prec = () => props.precision ?? 2;
   const timeData = createMemo(() => {
     const cpu = props.stats.time.cpu;
     const gc = props.stats.time.gc || 0;
@@ -45,7 +47,7 @@ const TimeChart: Component<TimeChartProps> = props => {
                   }}
                 />
               </div>
-              <div class="time-bar-value">{formatTime(item.value)}</div>
+              <div class="time-bar-value">{formatTime(item.value, prec())}</div>
             </div>
           )}
         </For>
@@ -59,11 +61,13 @@ const TimeChart: Component<TimeChartProps> = props => {
           </div>
           <div class="gc-stat">
             <span class="gc-stat-label">Heap Size</span>
-            <span class="gc-stat-value">{formatBytes(props.stats.gc?.heapSize || 0)}</span>
+            <span class="gc-stat-value">{formatBytes(props.stats.gc?.heapSize || 0, prec())}</span>
           </div>
           <div class="gc-stat">
             <span class="gc-stat-label">GC Fraction</span>
-            <span class="gc-stat-value">{formatPercent(props.stats.time.gcFraction || 0)}</span>
+            <span class="gc-stat-value">
+              {formatPercent(props.stats.time.gcFraction || 0, prec())}
+            </span>
           </div>
         </div>
       </Show>
diff --git a/packages/web/src/index.tsx b/packages/web/src/index.tsx
index a173b19..578bb8a 100644
--- a/packages/web/src/index.tsx
+++ b/packages/web/src/index.tsx
@@ -31,6 +31,7 @@ function App() {
   const [showSaveDialog, setShowSaveDialog] = createSignal(false);
   const [showHelp, setShowHelp] = createSignal(false);
   const [showManageSnapshots, setShowManageSnapshots] = createSignal(false);
+  const [precision, setPrecision] = createSignal(2);
   const [isLoading, setIsLoading] = createSignal(true);
 
   const STORAGE_KEY = 'ns-data';
@@ -58,6 +59,9 @@ function App() {
         if (parsed.view) {
           setView(parsed.view);
         }
+        if (typeof parsed.precision === 'number' && parsed.precision >= 0) {
+          setPrecision(parsed.precision);
+        }
       }
     } catch (e) {
       console.warn('Failed to load saved data:', e);
@@ -84,6 +88,7 @@ function App() {
       raw: Record<string, unknown> | null,
       snaps: ComparisonEntry[],
       v: 'analysis' | 'compare',
+      prec: number,
     ) => {
       try {
         localStorage.setItem(
@@ -93,6 +98,7 @@ function App() {
             currentStats: stats,
             currentRaw: raw,
             view: v,
+            precision: prec,
           }),
         );
       } catch (e) {
@@ -108,10 +114,11 @@ function App() {
     const raw = currentRaw();
     const snaps = snapshots();
     const v = view();
+    const prec = precision();
 
     if (isLoading()) return;
 
-    saveToStorage(stats, raw, snaps, v);
+    saveToStorage(stats, raw, snaps, v, prec);
   });
 
   const saveSnapshot = () => {
@@ -190,6 +197,16 @@ function App() {
               <Trash2Icon size={16} />
             </button>
           </Show>
+          <select
+            class="precision-select"
+            value={precision()}
+            onChange={e => setPrecision(parseInt(e.currentTarget.value, 10))}
+            title="Decimal Precision"
+          >
+            <For each={[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]}>
+              {p => <option value={p}>{p} dp</option>}
+            </For>
+          </select>
         </nav>
       </header>
 
@@ -213,7 +230,7 @@ function App() {
               />
             </Show>
             <Show when={currentStats()}>
-              <Analysis stats={currentStats()!} />
+              <Analysis stats={currentStats()!} precision={precision()} />
               <Show when={showSaveDialog()}>
                 <div class="modal-overlay" onClick={() => setShowSaveDialog(false)}>
                   <div class="modal" onClick={e => e.stopPropagation()}>
@@ -246,6 +263,7 @@ function App() {
               entries={snapshots()}
               onSelect={entry => setCurrentStats(entry.data)}
               onDelete={deleteSnapshot}
+              precision={precision()}
             />
           </Show>
         </Show>
diff --git a/packages/web/src/styles.css b/packages/web/src/styles.css
index 3a43b85..95e9806 100644
--- a/packages/web/src/styles.css
+++ b/packages/web/src/styles.css
@@ -1628,3 +1628,65 @@ body {
     display: none;
   }
 }
+
+.precision-select {
+  padding: 0.5rem 1.5rem 0.5rem 0.75rem;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border-color);
+  border-radius: 0.375rem;
+  color: var(--text-secondary);
+  font-size: 0.875rem;
+  cursor: pointer;
+  appearance: none;
+  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%239ca3af' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
+  background-repeat: no-repeat;
+  background-position: right 0.5rem center;
+}
+
+.precision-select:hover {
+  border-color: var(--text-muted);
+  color: var(--text-primary);
+}
+
+.precision-select:focus {
+  outline: none;
+  border-color: var(--accent);
+}
+
+.settings-label {
+  font-size: 0.875rem;
+  font-weight: 500;
+  color: var(--text-primary);
+}
+
+.precision-input {
+  width: 120px;
+  padding: 0.75rem 1rem;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border-color);
+  border-radius: 0.5rem;
+  color: var(--text-primary);
+  font-size: 0.9375rem;
+  text-align: center;
+}
+
+.precision-input:focus {
+  outline: none;
+  border-color: var(--accent);
+}
+
+/* Hide number input spinners */
+.precision-input::-webkit-outer-spin-button,
+.precision-input::-webkit-inner-spin-button {
+  -webkit-appearance: none;
+  margin: 0;
+}
+
+.precision-input[type='number'] {
+  -moz-appearance: textfield;
+}
+
+.settings-hint {
+  font-size: 0.75rem;
+  color: var(--text-muted);
+}