diff --git a/NanoVNASaver/SITools.py b/NanoVNASaver/SITools.py
index dcc019b..5ad2942 100644
--- a/NanoVNASaver/SITools.py
+++ b/NanoVNASaver/SITools.py
@@ -22,8 +22,8 @@ from decimal import Context, Decimal, InvalidOperation
 from typing import NamedTuple
 from numbers import Number, Real
 
-PREFIXES = ("y", "z", "a", "f", "p", "n", "µ", "m",
-            "", "k", "M", "G", "T", "P", "E", "Z", "Y")
+PREFIXES = ("q", "r", "y", "z", "a", "f", "p", "n", "µ", "m",
+            "", "k", "M", "G", "T", "P", "E", "Z", "Y", "R", "Q")
 
 
 def clamp_value(value: Real, rmin: Real, rmax: Real) -> Real:
@@ -56,8 +56,8 @@ class Format(NamedTuple):
     fix_decimals: bool = False
     space_str: str = ""
     assume_infinity: bool = True
-    min_offset: int = -8
-    max_offset: int = 8
+    min_offset: int = -10
+    max_offset: int = 10
     allow_strip: bool = False
     allways_signed: bool = False
     printable_min: float = -math.inf
@@ -71,11 +71,11 @@ class Format(NamedTuple):
 
 
 class Value:
-    CTX = Context(prec=60, Emin=-27, Emax=27)
+    CTX = Context(prec=60, Emin=-33, Emax=33)
 
     def __init__(self, value: Real = Decimal(0), unit: str = "", fmt=Format()):
         assert 1 <= fmt.max_nr_digits <= 30
-        assert -8 <= fmt.min_offset <= fmt.max_offset <= 8
+        assert -10 <= fmt.min_offset <= fmt.max_offset <= 10
         assert fmt.parse_clamp_min < fmt.parse_clamp_max
         assert fmt.printable_min < fmt.printable_max
         self._unit = unit
@@ -128,7 +128,7 @@ class Value:
         if self.fmt.allow_strip and "." in result:
             result = result.rstrip("0").rstrip(".")
 
-        return result + fmt.space_str + PREFIXES[offset + 8] + self._unit
+        return result + fmt.space_str + PREFIXES[offset + 10] + self._unit
 
     def __int__(self):
         return round(self._value)
@@ -163,7 +163,7 @@ class Value:
         if self.fmt.parse_sloppy_kilo and value[-1] in ("K", "m", "g"):
             value = value[:-1] + value[-1].swapcase()
         if value[-1] in PREFIXES:
-            factor = 10 ** ((PREFIXES.index(value[-1]) - 8) * 3)
+            factor = 10 ** ((PREFIXES.index(value[-1]) - 10) * 3)
             value = value[:-1]
 
         if self.fmt.assume_infinity and value == "\N{INFINITY}":
diff --git a/test/test_sitools.py b/test/test_sitools.py
index ca324b1..6521bf9 100644
--- a/test/test_sitools.py
+++ b/test/test_sitools.py
@@ -29,9 +29,9 @@ F_DEFAULT = Format()
 
 F_ASSERT_DIGITS_0 = Format(max_nr_digits=0)
 F_ASSERT_DIGITS_2 = Format(max_nr_digits=31)
-F_ASSERT_OFFSET_1 = Format(min_offset=-9)
-F_ASSERT_OFFSET_2 = Format(max_offset=9)
-F_ASSERT_OFFSET_3 = Format(min_offset=9)
+F_ASSERT_OFFSET_1 = Format(min_offset=-11)
+F_ASSERT_OFFSET_2 = Format(max_offset=11)
+F_ASSERT_OFFSET_3 = Format(min_offset=11)
 F_ASSERT_CLAMP = Format(parse_clamp_min=10, parse_clamp_max=9)
 
 F_DIGITS_1 = Format(max_nr_digits=1, min_offset=-2,
@@ -81,8 +81,10 @@ class TestSIToolsValue(unittest.TestCase):
         self.assertEqual(str(Value(1e18)), "1.00000E")
         self.assertEqual(str(Value(1e21)), "1.00000Z")
         self.assertEqual(str(Value(1e24)), "1.00000Y")
-        self.assertEqual(str(Value(1e27)), "\N{INFINITY}")
-        self.assertEqual(str(Value(-1e27)), "-\N{INFINITY}")
+        self.assertEqual(str(Value(1e27)), "1.00000R")
+        self.assertEqual(str(Value(1e30)), "1.00000Q")
+        self.assertEqual(str(Value(1e34)), "\N{INFINITY}")
+        self.assertEqual(str(Value(-1e34)), "-\N{INFINITY}")
         self.assertEqual(str(Value(nan)), "-")
         self.assertEqual(float(Value(1e27)), 1e27)
         self.assertEqual(
@@ -100,11 +102,13 @@ class TestSIToolsValue(unittest.TestCase):
         self.assertEqual(str(Value(1e-18)), "1.00000a")
         self.assertEqual(str(Value(1e-21)), "1.00000z")
         self.assertEqual(str(Value(1e-24)), "1.00000y")
-        self.assertEqual(str(Value(1e-27)), "0.00100y")
-        self.assertEqual(str(Value(1e-29)), "0.00001y")
-        self.assertEqual(str(Value(-1e-29)), "-0.00001y")
-        self.assertEqual(str(Value(1e-30)), "0.00000")
-        self.assertEqual(float(Value(1e-30)), 1e-30)
+        self.assertEqual(str(Value(1e-27)), "1.00000r")
+        self.assertEqual(str(Value(1e-30)), "1.00000q")
+        self.assertEqual(str(Value(1e-33)), "0.00100q")
+        self.assertEqual(str(Value(1e-35)), "0.00001q")
+        self.assertEqual(str(Value(-1e-35)), "-0.00001q")
+        self.assertEqual(str(Value(1e-36)), "0.00000")
+        self.assertEqual(float(Value(1e-36)), 1e-36)
 
     def test_format_digits_1(self):
         v = Value(fmt=F_DIGITS_1)