diff --git a/assets/calc/large-ints.yml b/assets/calc/large-ints.yml
new file mode 100644
index 00000000..509990cd
--- /dev/null
+++ b/assets/calc/large-ints.yml
@@ -0,0 +1,2 @@
+int: (( calc "90 * 86400" ))
+float: (( calc "(90 * 86400) + 0.1" ))
diff --git a/ci/release_notes.md b/ci/release_notes.md
new file mode 100644
index 00000000..b6d82479
--- /dev/null
+++ b/ci/release_notes.md
@@ -0,0 +1,9 @@
+# Bug Fixes
+
+- Fixed `((calc))` to output integer values for its output, when
+  the result is a large integer. Previously, it was treated as a float,
+  and converted to scientific notation by the YAML marshaler. Fixes #286.
+
+# Acknowledgements
+
+Thanks @jhunt for finding and reporting the issue!
diff --git a/cmd/spruce/main_test.go b/cmd/spruce/main_test.go
index 50509849..17bb1951 100644
--- a/cmd/spruce/main_test.go
+++ b/cmd/spruce/main_test.go
@@ -1298,6 +1298,18 @@ z:
 `)
 				So(stdout, ShouldEqual, "")
 			})
+
+			Convey("Calc returns int64s if possible", func() {
+				os.Args = []string{"spruce", "merge", "--prune", "meta", "../../assets/calc/large-ints.yml"}
+				stdout = ""
+				stderr = ""
+				main()
+				So(stderr, ShouldEqual, "")
+				So(stdout, ShouldEqual, `float: 7.776e+06
+int: 7776000
+
+`)
+			})
 		})
 
 		Convey("YAML output is ordered the same way each time (#184)", func() {
diff --git a/op_calc.go b/op_calc.go
index e65844f7..04546b48 100644
--- a/op_calc.go
+++ b/op_calc.go
@@ -86,6 +86,13 @@ func (CalcOperator) Run(ev *Evaluator, args []*Expr) (*Response, error) {
 			return nil, evaluateError
 		}
 
+		if resultFloat, ok := result.(float64); ok {
+			resultInt := int64(resultFloat)
+			if float64(resultInt) == resultFloat {
+				result = resultInt
+			}
+		}
+
 		DEBUG("  evaluated result: %v", result)
 		return &Response{
 			Type:  Replace,