diff --git a/src/scgenerator/variableparameters.py b/src/scgenerator/variableparameters.py
index bbf08cd..5bb3d3e 100644
--- a/src/scgenerator/variableparameters.py
+++ b/src/scgenerator/variableparameters.py
@@ -21,6 +21,7 @@ class Variable(Generic[T]):
     all_nums: list[int]
     suffix: str = ""
     decimals: int = 4
+    format_str: str | None = None
     formatter: Callable[[int], str] = field(init=False)
 
     def __getstate__(self):
@@ -31,7 +32,10 @@ class Variable(Generic[T]):
         self.__post_init__()
 
     def __post_init__(self):
-        self.formatter = unit_formatter(self.suffix, self.decimals)
+        if self.format_str is not None:
+            self.formatter = lambda v: format(v, self.format_str)
+        else:
+            self.formatter = unit_formatter(self.suffix, self.decimals)
 
     def __call__(self, id: int, local: bool = False) -> T:
         if id < 0:
@@ -61,6 +65,7 @@ class VariableParameter:
     default: float | int | None = None
     suffix: str = ""
     decimals: int = 4
+    format_str: str | None = None
     sync: VariableParameter | None = None
     auto_sync: bool = False
     default_sequence: Variable | None = field(init=False)
@@ -96,6 +101,7 @@ class VariableParameter:
             place=self.place,
             suffix=self.suffix,
             decimals=self.decimals,
+            format_str=self.format_str,
             all_nums=all_nums,
         )
         all_nums[self.place] = len(var_obj)
@@ -132,6 +138,7 @@ class VariableParameter:
             place=self.place,
             suffix=self.suffix,
             decimals=self.decimals,
+            format_str=self.format_str,
             all_nums=all_nums,
         )
         all_nums[self.place] = len(obj)
@@ -348,12 +355,18 @@ def vfield(
     default: float | int | None = None,
     suffix: str = "",
     decimals: int = 4,
+    format_str: str | None = None,
     sync: VariableParameter | None = None,
     auto_sync: bool = False,
 ):
     return field(
         default=VariableParameter(
-            default, suffix, decimals, sync.default if sync is not None else None, auto_sync
+            default=default,
+            suffix=suffix,
+            decimals=decimals,
+            format_str=format_str,
+            sync=sync.default if sync is not None else None,
+            auto_sync=auto_sync,
         )
     )
 
diff --git a/tests/test_variableparameters.py b/tests/test_variableparameters.py
index b46958f..c09a264 100644
--- a/tests/test_variableparameters.py
+++ b/tests/test_variableparameters.py
@@ -292,6 +292,21 @@ def test_unit_forammter():
     assert fmt(np.zeros((2, 2, 2))) == "(((0, 0), (0, 0)), ((0, 0), (0, 0)))"
 
 
+def test_format_str():
+    """format_str takes precedence"""
+
+    @vdataclass
+    class Conf:
+        x: Variable = vfield(default=123456789)
+        y: Variable = vfield(default=123456789, decimals=2)
+        z: Variable = vfield(default=123456789, decimals=2, format_str="d")
+
+    conf = Conf()
+    assert conf.x.format(0) == "x=1.235e+08"
+    assert conf.y.format(0) == "y=1.2e+08"
+    assert conf.z.format(0) == "z=123456789"
+
+
 def test_param_formatting():
     """formatting is always respected"""