diff --git a/opm/io/eclipse/EclFile.hpp b/opm/io/eclipse/EclFile.hpp
index 34a77f46d..1fb57c432 100644
--- a/opm/io/eclipse/EclFile.hpp
+++ b/opm/io/eclipse/EclFile.hpp
@@ -64,6 +64,7 @@ public:
     bool hasKey(const std::string &name) const;
 
     const std::vector<std::string>& arrayNames() const { return array_name; }
+    std::size_t size() const;
 
 protected:
     bool formatted;
diff --git a/src/opm/io/eclipse/EclFile.cpp b/src/opm/io/eclipse/EclFile.cpp
index 9d3a6d6ee..c66537d62 100644
--- a/src/opm/io/eclipse/EclFile.cpp
+++ b/src/opm/io/eclipse/EclFile.cpp
@@ -898,4 +898,10 @@ const std::vector<std::string>& EclFile::get<std::string>(const std::string &nam
     return getImpl(search->second, CHAR, char_array, "string");
 }
 
+
+std::size_t EclFile::size() const {
+    return this->array_name.size();
+}
+
+
 }} // namespace Opm::ecl
diff --git a/tests/test_EclIO.cpp b/tests/test_EclIO.cpp
index 07697f5de..75a00b52b 100644
--- a/tests/test_EclIO.cpp
+++ b/tests/test_EclIO.cpp
@@ -272,6 +272,8 @@ BOOST_AUTO_TEST_CASE(TestEcl_Write_formatted_not_finite) {
     BOOST_CHECK(std::isinf(d[0]));
     BOOST_CHECK(std::isnan(f[1]));
     BOOST_CHECK(std::isnan(d[1]));
+
+    BOOST_CHECK_EQUAL(file1.size(), 2);
 }