diff --git a/go.mod b/go.mod
index 910022d..5aea054 100644
--- a/go.mod
+++ b/go.mod
@@ -3,12 +3,12 @@ module github.com/sdcoffey/techan
 go 1.21
 
 require (
-	github.com/sdcoffey/big v0.7.0
-	github.com/stretchr/testify v1.7.0
+	github.com/sdcoffey/big v0.8.0
+	github.com/stretchr/testify v1.11.1
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index d195378..768cc6e 100644
--- a/go.sum
+++ b/go.sum
@@ -1,15 +1,12 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/sdcoffey/big v0.7.0 h1:OnE7fcHq/C59WxWrMegftFa1nftCjsZLVf7PLXsxj2Y=
-github.com/sdcoffey/big v0.7.0/go.mod h1:2T05Q7Mt6F1kHHb+PFa0odPFwU67YnSAFYgiYy7krPU=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.1.4/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
-github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/sdcoffey/big v0.8.0 h1:njCAnzEHdWUfYBK6Jj9NowXpIaE3p+s2S4qjlh/wn5I=
+github.com/sdcoffey/big v0.8.0/go.mod h1:o0blP3VmRolJhiftTQnhwH+gUzqFPSXDDshA6Ddc854=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/rule_stop.go b/rule_stop.go
index 66d0bf1..2ea19c3 100644
--- a/rule_stop.go
+++ b/rule_stop.go
@@ -1,6 +1,10 @@
 package techan
 
-import "github.com/sdcoffey/big"
+import (
+	"strconv"
+
+	"github.com/sdcoffey/big"
+)
 
 type stopLossRule struct {
 	Indicator
@@ -12,7 +16,7 @@ type stopLossRule struct {
 func NewStopLossRule(series *TimeSeries, lossTolerance float64) Rule {
 	return stopLossRule{
 		Indicator: NewClosePriceIndicator(series),
-		tolerance: big.NewDecimal(lossTolerance),
+		tolerance: big.NewFromString(strconv.FormatFloat(lossTolerance, 'f', -1, 64)),
 	}
 }
 
@@ -25,9 +29,9 @@ func (slr stopLossRule) IsSatisfied(index int, record *TradingRecord) bool {
 	currentPrice := slr.Indicator.Calculate(index)
 	entryPrice := entryOrder.Price
 
-	loss := currentPrice.Div(entryPrice).Sub(big.ONE)
+	loss := currentPrice.Sub(entryPrice).Div(entryPrice)
 	if entryOrder.Side == SELL {
-		loss = big.ONE.Sub(currentPrice.Div(entryPrice))
+		loss = entryPrice.Sub(currentPrice).Div(entryPrice)
 	}
 
 	return loss.LTE(slr.tolerance)