Added method to get number of children.

src/TilesMath/LocalMath.cs

@@ -0,0 +1,9 @@
+namespace TilesMath;
+
+internal static class LocalMath
+{
+    public static int SimplePower(int x, int pow)
+    {
+        return (int)Math.Pow(x, pow);
+    }
+}

src/TilesMath/Tile.cs

@@ -129,6 +129,24 @@ public IEnumerable<Tile> ChildrenAtZoom(int zoom, Func<Tile, bool>? exclude = nu
         }
     }
 
+    /// <summary>
+    /// Returns the number of children at the given zoom level.
+    /// </summary>
+    /// <param name="zoom">The zoom level.</param>
+    /// <returns></returns>
+    public long ChildrenAtZoomCount(int zoom)
+    {
+        if (zoom < this.Zoom) throw new Exception("Cannot calculate sub tiles for a smaller zoom level");
+
+        if (zoom == this.Zoom)
+        {
+            return 1;
+        }
+
+        var diff = zoom - this.Zoom;
+        return LocalMath.SimplePower(4, diff);
+    }
+
     public bool Equals(Tile other)
     {
         return this.X == other.X && this.Y == other.Y && this.Zoom == other.Zoom;

src/TilesMath/TilesMath.csproj

@@ -4,7 +4,7 @@
     <TargetFramework>net6.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <PackageVersion>0.0.10</PackageVersion>
+    <PackageVersion>0.0.11</PackageVersion>
     <Title>TilesMath</Title>
     <Authors>ANYWAYS BV</Authors>
     <Description>A tiny library for tiles math.</Description>

test/TilesMath.Tests/TileTests.cs

@@ -28,4 +28,37 @@ public void Tile_ParentAt_5ZoomsUp_ShouldEqual5thParentUp()
         var parent = tile.Parent?.Parent?.Parent?.Parent?.Parent ?? throw new Exception("No parent");
         Assert.Equal(parent, tile.ParentAt(tile.Zoom - 5));
     }
+
+    [Fact]
+    public void Tile_ChildrenAtZoomCount_SameZoom_ShouldEqual1()
+    {
+        var tile = Tile.Create(1025, 4511, 14);
+
+        Assert.Equal(1, tile.ChildrenAtZoomCount(14));
+    }
+
+    [Fact]
+    public void Tile_ChildrenAtZoomCount_Zoom1Higher_ShouldEqual4()
+    {
+        var tile = Tile.Create(1025, 4511, 14);
+
+        Assert.Equal(4, tile.ChildrenAtZoomCount(15));
+    }
+
+    [Fact]
+    public void Tile_ChildrenAtZoomCount_Zoom2Higher_ShouldEqual16()
+    {
+        var tile = Tile.Create(1025, 4511, 14);
+
+        Assert.Equal(16, tile.ChildrenAtZoomCount(16));
+    }
+
+    [Fact]
+    public void Tile_ChildrenAtZoomCount_Zoom0_ShouldEqual4ToThePowerOfZoom()
+    {
+        var tile = Tile.Create(0, 0, 0);
+
+        Assert.Equal((int)Math.Pow(4, 14), tile.ChildrenAtZoomCount(14));
+        Assert.Equal((int)Math.Pow(4, 5), tile.ChildrenAtZoomCount(5));
+    }
 }