diff --git a/src/dsc.h b/src/dsc.h
index c2c29414..5995dcb0 100644
--- a/src/dsc.h
+++ b/src/dsc.h
@@ -493,4 +493,19 @@ public:
     }
 };
 
+class BBox {
+public:
+    Vector minp;
+    Vector maxp;
+
+    BBox();
+    BBox(const Vector &p0, const Vector &p1);
+
+    Vector GetOrigin();
+    Vector GetExtents();
+
+    void Include(const Vector &v, double r = 0.0);
+    bool Overlaps(BBox &b1);
+};
+
 #endif
diff --git a/src/solvespace.cpp b/src/solvespace.cpp
index d9c343fb..fdc3d45f 100644
--- a/src/solvespace.cpp
+++ b/src/solvespace.cpp
@@ -817,3 +817,37 @@ void Sketch::Clear(void) {
     entity.Clear();
     param.Clear();
 }
+
+BBox Sketch::CalculateEntityBBox(bool includingInvisible) {
+    BBox box;
+    bool first = true;
+    for(int i = 0; i < entity.n; i++) {
+        Entity *e = (Entity *)&entity.elem[i];
+        if(!(e->IsVisible() || includingInvisible)) continue;
+
+        Vector point;
+        double r = 0.0;
+        if(e->IsPoint()) {
+            point = e->PointGetNum();
+        } else {
+            switch(e->type) {
+                case Entity::ARC_OF_CIRCLE:
+                case Entity::CIRCLE:
+                    r = e->CircleGetRadiusNum();
+                    point = GetEntity(e->point[0])->PointGetNum();
+                    break;
+                default: continue;
+            }
+        }
+
+        if(first) {
+            box.minp = point;
+            box.maxp = point;
+            box.Include(point, r);
+            first = false;
+        } else {
+            box.Include(point, r);
+        }
+    }
+    return box;
+}
diff --git a/src/solvespace.h b/src/solvespace.h
index 1be244ac..4ee1775f 100644
--- a/src/solvespace.h
+++ b/src/solvespace.h
@@ -701,6 +701,8 @@ public:
     // Styles are handled a bit differently.
 
     void Clear(void);
+
+    BBox CalculateEntityBBox(bool includingInvisible);
 };
 #undef ENTITY
 #undef CONSTRAINT
diff --git a/src/util.cpp b/src/util.cpp
index 959026cb..4cf1eca6 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -1047,3 +1047,34 @@ bool Point2d::Equals(Point2d v, double tol) {
     return (this->Minus(v)).MagSquared() < tol*tol;
 }
 
+BBox::BBox() { }
+BBox::BBox(const Vector &p0, const Vector &p1) {
+    minp.x = min(p0.x, p1.x);
+    minp.y = min(p0.y, p1.y);
+    minp.z = min(p0.z, p1.z);
+
+    maxp.x = max(p0.x, p1.x);
+    maxp.y = max(p0.y, p1.y);
+    maxp.z = max(p0.z, p1.z);
+}
+
+Vector BBox::GetOrigin() { return minp.Plus(maxp.Minus(minp)).ScaledBy(0.5); }
+Vector BBox::GetExtents() { return maxp.Minus(minp).ScaledBy(0.5); }
+
+void BBox::Include(const Vector &v, double r) {
+    minp.x = min(minp.x, v.x - r);
+    minp.y = min(minp.y, v.y - r);
+    minp.z = min(minp.z, v.z - r);
+
+    maxp.x = max(maxp.x, v.x + r);
+    maxp.y = max(maxp.y, v.y + r);
+    maxp.z = max(maxp.z, v.z + r);
+}
+
+bool BBox::Overlaps(BBox &b1) {
+
+    Vector t = b1.GetOrigin().Minus(GetOrigin());
+    Vector e = b1.GetExtents().Plus(GetExtents());
+
+    return fabs(t.x) < e.x && fabs(t.y) < e.y && fabs(t.z) < e.z;
+}