diff --git a/jmbitcoin/jmbitcoin/amount.py b/jmbitcoin/jmbitcoin/amount.py
index ff3d6cc..15e0de1 100644
--- a/jmbitcoin/jmbitcoin/amount.py
+++ b/jmbitcoin/jmbitcoin/amount.py
@@ -39,7 +39,7 @@ def amount_to_sat_str(amount_str):
 
 
 def amount_to_btc_str(amount_str):
-    return str(amount_to_btc(amount_str)) + " BTC"
+    return '%.8f' % amount_to_btc(amount_str) + " BTC"
 
 
 def amount_to_str(amount_str):
diff --git a/jmbitcoin/test/test_amounts.py b/jmbitcoin/test/test_amounts.py
new file mode 100644
index 0000000..1944eec
--- /dev/null
+++ b/jmbitcoin/test/test_amounts.py
@@ -0,0 +1,94 @@
+import jmbitcoin as btc
+import pytest
+from decimal import Decimal
+
+
+def test_btc_to_sat():
+    assert(btc.btc_to_sat(Decimal("0.00000001")) == 1)
+    assert(btc.btc_to_sat(Decimal("1.00000000")) == 100000000)
+
+
+def test_sat_to_btc():
+    assert(btc.sat_to_btc(1) == Decimal("0.00000001"))
+    assert(btc.sat_to_btc(100000000) == Decimal("1.00000000"))
+
+
+def test_amount_to_sat():
+    assert(btc.amount_to_sat("1") == 1)
+    assert(btc.amount_to_sat("1sat") == 1)
+    assert(btc.amount_to_sat("1.123sat") == 1)
+    assert(btc.amount_to_sat("0.00000001") == 1)
+    assert(btc.amount_to_sat("0.00000001btc") == 1)
+    assert(btc.amount_to_sat("0.00000001BTC") == 1)
+    assert(btc.amount_to_sat("1.00000000") == 100000000)
+    assert(btc.amount_to_sat("1.12300000sat") == 1)
+    assert(btc.amount_to_sat("1btc") == 100000000)
+    assert(btc.amount_to_sat("1BTC") == 100000000)
+
+
+def test_amount_to_btc():
+    assert(btc.amount_to_btc("1") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("1sat") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("1.123sat") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("0.00000001") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("0.00000001btc") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("0.00000001BTC") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("1.00000000") == 1)
+    assert(btc.amount_to_btc("1.12300000sat") == Decimal("0.00000001"))
+    assert(btc.amount_to_btc("1btc") == 1)
+    assert(btc.amount_to_btc("1BTC") == 1)
+
+
+def test_amount_to_sat_str():
+    assert(btc.amount_to_sat_str("1") == "1 sat")
+    assert(btc.amount_to_sat_str("1sat") == "1 sat")
+    assert(btc.amount_to_sat_str("1.123sat") == "1 sat")
+    assert(btc.amount_to_sat_str("0.00000001") == "1 sat")
+    assert(btc.amount_to_sat_str("0.00000001btc") == "1 sat")
+    assert(btc.amount_to_sat_str("0.00000001BTC") == "1 sat")
+    assert(btc.amount_to_sat_str("1.00000000") == "100000000 sat")
+    assert(btc.amount_to_sat_str("1.12300000sat") == "1 sat")
+    assert(btc.amount_to_sat_str("1btc") == "100000000 sat")
+    assert(btc.amount_to_sat_str("1BTC") == "100000000 sat")
+
+
+def test_amount_to_btc_str():
+    assert(btc.amount_to_btc_str("1") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("1sat") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("1.123sat") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("0.00000001") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("0.00000001btc") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("0.00000001BTC") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("1.00000000") == "1.00000000 BTC")
+    assert(btc.amount_to_btc_str("1.12300000sat") == "0.00000001 BTC")
+    assert(btc.amount_to_btc_str("1btc") == "1.00000000 BTC")
+    assert(btc.amount_to_btc_str("1BTC") == "1.00000000 BTC")
+
+
+def test_amount_to_str():
+    assert(btc.amount_to_str("1") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("1sat") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("1.123sat") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("0.00000001") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("0.00000001btc") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("0.00000001BTC") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("1.00000000") == "1.00000000 BTC (100000000 sat)")
+    assert(btc.amount_to_str("1.12300000sat") == "0.00000001 BTC (1 sat)")
+    assert(btc.amount_to_str("1btc") == "1.00000000 BTC (100000000 sat)")
+    assert(btc.amount_to_str("1BTC") == "1.00000000 BTC (100000000 sat)")
+
+
+def test_sat_to_str():
+    assert(btc.sat_to_str(1) == "0.00000001")
+    assert(btc.sat_to_str(100000000) == "1.00000000")
+
+
+def test_sat_to_str_p():
+    assert(btc.sat_to_str_p(1) == "+0.00000001")
+    assert(btc.sat_to_str_p(-1) == "-0.00000001")
+    assert(btc.sat_to_str_p(100000000) == "+1.00000000")
+    assert(btc.sat_to_str_p(-100000000) == "-1.00000000")
+
+
+def test_fee_per_kb_to_str():
+    assert(btc.fee_per_kb_to_str(1000) == "1000 sat/vkB (1.0 sat/vB)")