diff --git a/parcels/compilation/codecompiler.py b/parcels/compilation/codecompiler.py
index 406daf597..bcc508897 100644
--- a/parcels/compilation/codecompiler.py
+++ b/parcels/compilation/codecompiler.py
@@ -110,7 +110,7 @@ def __init__(self, cppargs=None, ldargs=None, incdirs=None, libdirs=None, libs=N
         self._ldargs += lflags
         self._ldargs += ldargs
         if len(Lflags) > 0:
-            self._ldargs += ["-Wl, -rpath=%s" % (":".join(libdirs))]
+            self._ldargs += [f"-Wl, -rpath={':'.join(libdirs)}"]
         self._ldargs += arch_flag
         self._incdirs = incdirs
         self._libdirs = libdirs
diff --git a/parcels/compilation/codegenerator.py b/parcels/compilation/codegenerator.py
index 2569dcc6c..acce0f7dc 100644
--- a/parcels/compilation/codegenerator.py
+++ b/parcels/compilation/codegenerator.py
@@ -32,7 +32,7 @@ def __getattr__(self, attr):
         elif isinstance(getattr(self.obj, attr), VectorField):
             return VectorFieldNode(getattr(self.obj, attr), ccode=f"{self.ccode}->{attr}")
         else:
-            return ConstNode(getattr(self.obj, attr), ccode="%s" % (attr))
+            return ConstNode(getattr(self.obj, attr), ccode=f"{attr}")
 
 
 class FieldNode(IntrinsicNode):
@@ -480,13 +480,13 @@ def visit_FunctionDef(self, node):
             c.Value("double", "time"),
         ]
         for field in self.field_args.values():
-            args += [c.Pointer(c.Value("CField", "%s" % field.ccode_name))]
+            args += [c.Pointer(c.Value("CField", f"{field.ccode_name}"))]
         for field in self.vector_field_args.values():
             for fcomponent in ["U", "V", "W"]:
                 try:
                     f = getattr(field, fcomponent)
                     if f.ccode_name not in self.field_args:
-                        args += [c.Pointer(c.Value("CField", "%s" % f.ccode_name))]
+                        args += [c.Pointer(c.Value("CField", f"{f.ccode_name}"))]
                         self.field_args[f.ccode_name] = f
                 except:
                     pass  # field.W does not always exist
@@ -519,9 +519,9 @@ def visit_Call(self, node):
         if isinstance(node.func, PrintNode):
             # Write our own Print parser because Python3-AST does not seem to have one
             if isinstance(node.args[0], ast.Str):
-                node.ccode = str(c.Statement('printf("%s\\n")' % (node.args[0].s)))
+                node.ccode = str(c.Statement(f'printf("{node.args[0].s}\\n")'))
             elif isinstance(node.args[0], ast.Name):
-                node.ccode = str(c.Statement('printf("%%f\\n", %s)' % (node.args[0].id)))
+                node.ccode = str(c.Statement(f'printf("%f\\n", {node.args[0].id})'))
             elif isinstance(node.args[0], ast.BinOp):
                 if hasattr(node.args[0].right, "ccode"):
                     args = node.args[0].right.ccode
@@ -536,12 +536,12 @@ def visit_Call(self, node):
                             args.append(a.id)
                 else:
                     args = []
-                s = 'printf("%s\\n"' % node.args[0].left.s
+                s = f'printf("{node.args[0].left.s}\\n"'
                 if isinstance(args, str):
-                    s = s + (", %s)" % args)
+                    s = s + f", {args})"
                 else:
                     for arg in args:
-                        s = s + (", %s" % arg)
+                        s = s + (f", {arg}")
                     s = s + ")"
                 node.ccode = str(c.Statement(s))
             else:
@@ -559,7 +559,7 @@ def visit_Call(self, node):
                 elif isinstance(a, ParticleNode):
                     continue
                 elif pointer_args:
-                    a.ccode = "&%s" % a.ccode
+                    a.ccode = f"&{a.ccode}"
             ccode_args = ", ".join([a.ccode for a in node.args[pointer_args:]])
             try:
                 if isinstance(node.func, str):
@@ -733,7 +733,7 @@ def visit_BoolOp(self, node):
         self.visit(node.op)
         for v in node.values:
             self.visit(v)
-        op_str = " %s " % node.op.ccode
+        op_str = f" {node.op.ccode} "
         node.ccode = op_str.join([v.ccode for v in node.values])
 
     def visit_Eq(self, node):
@@ -804,7 +804,7 @@ def visit_ConstNode(self, node):
 
     def visit_Return(self, node):
         self.visit(node.value)
-        node.ccode = c.Statement("return %s" % node.value.ccode)
+        node.ccode = c.Statement(f"return {node.value.ccode}")
 
     def visit_FieldEvalNode(self, node):
         self.visit(node.field)
@@ -900,16 +900,16 @@ def visit_Print(self, node):
         for n in node.values:
             self.visit(n)
         if hasattr(node.values[0], "s"):
-            node.ccode = c.Statement('printf("%s\\n")' % (n.ccode))
+            node.ccode = c.Statement(f'printf("{n.ccode}\\n")')
             return
         if hasattr(node.values[0], "s_print"):
             args = node.values[0].right.ccode
-            s = 'printf("%s\\n"' % node.values[0].left.ccode
+            s = f'printf("{node.values[0].left.ccode}\\n"'
             if isinstance(args, str):
-                s = s + (", %s)" % args)
+                s = s + f", {args})"
             else:
                 for arg in args:
-                    s = s + (", %s" % arg)
+                    s = s + (f", {arg}")
                 s = s + ")"
             node.ccode = c.Statement(s)
             return
@@ -964,7 +964,7 @@ def generate(self, funcname, field_args, const_args, kernel_ast, c_include):
             c.Value("double", "dt"),
         ]
         for field, _ in field_args.items():
-            args += [c.Pointer(c.Value("CField", "%s" % field))]
+            args += [c.Pointer(c.Value("CField", f"{field}"))]
         for const, _ in const_args.items():
             args += [c.Value("double", const)]  # are we SURE those const's are double's ?
         fargs_str = ", ".join(["particles->time_nextloop[pnum]"] + list(field_args.keys()) + list(const_args.keys()))
diff --git a/parcels/fieldset.py b/parcels/fieldset.py
index fda0d4701..3f02cad20 100644
--- a/parcels/fieldset.py
+++ b/parcels/fieldset.py
@@ -1220,7 +1220,7 @@ def from_parcels(
         extra_fields.update({"U": uvar, "V": vvar})
         for vars in extra_fields:
             dimensions[vars] = deepcopy(default_dims)
-            dimensions[vars]["depth"] = "depth%s" % vars.lower()
+            dimensions[vars]["depth"] = f"depth{vars.lower()}"
         filenames = {v: str(f"{basename}{v}.nc") for v in extra_fields.keys()}
         return cls.from_netcdf(
             filenames,
diff --git a/parcels/kernel.py b/parcels/kernel.py
index b144abc72..37578af71 100644
--- a/parcels/kernel.py
+++ b/parcels/kernel.py
@@ -128,7 +128,7 @@ def _cache_key(self):
             field_keys = "-".join(
                 [f"{name}:{field.units.__class__.__name__}" for name, field in self.field_args.items()]
             )
-        key = self.name + self.ptype._cache_key + field_keys + ("TIME:%f" % ostime())
+        key = self.name + self.ptype._cache_key + field_keys + (f"TIME:{ostime():f}")
         return hashlib.md5(key.encode("utf-8")).hexdigest()
 
     def remove_deleted(self, pset):
@@ -304,7 +304,7 @@ def _cache_key(self):
             field_keys = "-".join(
                 [f"{name}:{field.units.__class__.__name__}" for name, field in self.field_args.items()]
             )
-        key = self.name + self.ptype._cache_key + field_keys + ("TIME:%f" % ostime())
+        key = self.name + self.ptype._cache_key + field_keys + (f"TIME:{ostime():f}")
         return hashlib.md5(key.encode("utf-8")).hexdigest()
 
     def add_scipy_positionupdate_kernels(self):
@@ -435,7 +435,7 @@ def get_kernel_compile_files(self):
                 self._cache_key
             )  # only required here because loading is done by Kernel class instead of Compiler class
             dyn_dir = get_cache_dir()
-            basename = "%s_0" % cache_name
+            basename = f"{cache_name}_0"
         lib_path = "lib" + basename
         src_file_or_files = None
         if type(basename) in (list, dict, tuple, ndarray):
diff --git a/parcels/particle.py b/parcels/particle.py
index cd524275b..dbb0c7f60 100644
--- a/parcels/particle.py
+++ b/parcels/particle.py
@@ -39,13 +39,13 @@ def __get__(self, instance, cls):
         if issubclass(cls, JITParticle):
             return instance._cptr.__getitem__(self.name)
         else:
-            return getattr(instance, "_%s" % self.name, self.initial)
+            return getattr(instance, f"_{self.name}", self.initial)
 
     def __set__(self, instance, value):
         if isinstance(instance, JITParticle):
             instance._cptr.__setitem__(self.name, value)
         else:
-            setattr(instance, "_%s" % self.name, value)
+            setattr(instance, f"_{self.name}", value)
 
     def __repr__(self):
         return f"PVar<{self.name}|{self.dtype}>"
diff --git a/parcels/particlefile.py b/parcels/particlefile.py
index 6e047130b..0aa61e349 100644
--- a/parcels/particlefile.py
+++ b/parcels/particlefile.py
@@ -121,7 +121,7 @@ def __init__(self, name, particleset, outputdt=np.inf, chunks=None, create_new_z
                         f"The ParticleFile name contains .zarr extension, but zarr files will be written per processor in MPI mode at {self.fname}"
                     )
             else:
-                self.fname = name if extension in [".zarr"] else "%s.zarr" % name
+                self.fname = name if extension in [".zarr"] else f"{name}.zarr"
 
     def _create_variables_attribute_dict(self):
         """Creates the dictionary with variable attributes.
@@ -209,7 +209,7 @@ def write(self, pset, time, indices=None):
         time = time.total_seconds() if isinstance(time, timedelta) else time
 
         if pset.particledata._ncount == 0:
-            logger.warning("ParticleSet is empty on writing as array at time %g" % time)
+            logger.warning(f"ParticleSet is empty on writing as array at time {time:g}")
             return
 
         if indices is None:
diff --git a/parcels/rng.py b/parcels/rng.py
index 602e5c874..bac7fbce8 100644
--- a/parcels/rng.py
+++ b/parcels/rng.py
@@ -95,7 +95,7 @@ def remove_lib(self):
 
     def compile(self, compiler=None):
         if self.src_file is None or self.lib_file is None or self.log_file is None:
-            basename = "parcels_random_%s" % uuid.uuid4()
+            basename = f"parcels_random_{uuid.uuid4()}"
             lib_filename = "lib" + basename
             basepath = os.path.join(get_cache_dir(), f"{basename}")
             libpath = os.path.join(get_cache_dir(), f"{lib_filename}")
diff --git a/parcels/tools/converters.py b/parcels/tools/converters.py
index c8ccf8003..bef13d14e 100644
--- a/parcels/tools/converters.py
+++ b/parcels/tools/converters.py
@@ -135,7 +135,7 @@ def fulltime(self, time):
             raise RuntimeError(f"Calendar {self.calendar} not implemented in TimeConverter")
 
     def __repr__(self):
-        return "%s" % self.time_origin
+        return f"{self.time_origin}"
 
     def __eq__(self, other):
         other = other.time_origin if isinstance(other, TimeConverter) else other
@@ -217,10 +217,10 @@ def to_source(self, value, x, y, z):
         return value * 1000.0 * 1.852 * 60.0 * cos(y * pi / 180)
 
     def ccode_to_target(self, x, y, z):
-        return "(1.0 / (1000. * 1.852 * 60. * cos(%s * M_PI / 180)))" % y
+        return f"(1.0 / (1000. * 1.852 * 60. * cos({y} * M_PI / 180)))"
 
     def ccode_to_source(self, x, y, z):
-        return "(1000. * 1.852 * 60. * cos(%s * M_PI / 180))" % y
+        return f"(1000. * 1.852 * 60. * cos({y} * M_PI / 180))"
 
 
 class GeographicSquare(UnitConverter):
@@ -257,10 +257,10 @@ def to_source(self, value, x, y, z):
         return value * pow(1000.0 * 1.852 * 60.0 * cos(y * pi / 180), 2)
 
     def ccode_to_target(self, x, y, z):
-        return "pow(1.0 / (1000. * 1.852 * 60. * cos(%s * M_PI / 180)), 2)" % y
+        return f"pow(1.0 / (1000. * 1.852 * 60. * cos({y} * M_PI / 180)), 2)"
 
     def ccode_to_source(self, x, y, z):
-        return "pow((1000. * 1.852 * 60. * cos(%s * M_PI / 180)), 2)" % y
+        return f"pow((1000. * 1.852 * 60. * cos({y} * M_PI / 180)), 2)"
 
 
 unitconverters_map = {
diff --git a/parcels/tools/global_statics.py b/parcels/tools/global_statics.py
index 0e97bac0d..381efc363 100644
--- a/parcels/tools/global_statics.py
+++ b/parcels/tools/global_statics.py
@@ -34,6 +34,6 @@ def get_package_dir():
 
 
 def get_cache_dir():
-    directory = os.path.join(gettempdir(), "parcels-%s" % getuid())
+    directory = os.path.join(gettempdir(), f"parcels-{getuid()}")
     Path(directory).mkdir(exist_ok=True)
     return directory
diff --git a/parcels/tools/timer.py b/parcels/tools/timer.py
index 02daf75ab..4a93c03dd 100644
--- a/parcels/tools/timer.py
+++ b/parcels/tools/timer.py
@@ -50,7 +50,7 @@ def print_tree_sequential(self, step=0, root_time=0, parent_time=0):
         print("  " * (step + 1), end="")
         if step > 0:
             print("(%3d%%) " % round(time / parent_time * 100), end="")
-        t_str = "%1.3e s" % time if root_time < 300 else datetime.timedelta(seconds=time)
+        t_str = f"{time:1.3e} s" if root_time < 300 else datetime.timedelta(seconds=time)
         print(f"Timer {(self._name).ljust(20 - 2*step + 7*(step == 0))}: {t_str}")
         for child in self._children:
             child.print_tree_sequential(step + 1, root_time, time)
diff --git a/pyproject.toml b/pyproject.toml
index d42401fbe..64f1927a9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -66,7 +66,7 @@ select = [
     "F",  # pyflakes
     "I",  # isort
     "B",  # Bugbear
-    # "UP", # pyupgrade
+    "UP", # pyupgrade
     "LOG", # logging
     "ICN", # import conventions
     "G", # logging-format
diff --git a/tests/test_kernel_language.py b/tests/test_kernel_language.py
index 19ca2289a..ec3a20da0 100644
--- a/tests/test_kernel_language.py
+++ b/tests/test_kernel_language.py
@@ -277,7 +277,7 @@ def kernel(particle, fieldset, time):
 
     def kernel2(particle, fieldset, time):
         tmp = 3
-        print("%f" % (tmp))
+        print(f"{tmp:f}")
 
     pset.execute(kernel2, endtime=2.0, dt=1.0, verbose_progress=False)
     out, err = capfd.readouterr()