diff --git a/src/export.cpp b/src/export.cpp
index 46ab076..f670f1b 100644
--- a/src/export.cpp
+++ b/src/export.cpp
@@ -890,7 +890,7 @@ void SolveSpaceUI::ExportMeshAsThreeJsTo(FILE *f, const std::string &filename,
     if(lastSlash == std::string::npos) oops();
     baseFilename.erase(0, lastSlash + 1);
 
-    for(int i = 0; i < baseFilename.length(); i++) {
+    for(size_t i = 0; i < baseFilename.length(); i++) {
         if(!isalpha(baseFilename[i]) &&
            /* also permit UTF-8 */ !((unsigned char)baseFilename[i] >= 0x80))
             baseFilename[i] = '_';
diff --git a/src/file.cpp b/src/file.cpp
index 61d1c24..a404f93 100644
--- a/src/file.cpp
+++ b/src/file.cpp
@@ -695,13 +695,13 @@ static std::string MakePathRelative(const std::string &base, const std::string &
                              resultParts;
     baseParts.pop_back();
 
-    int common;
+    size_t common;
     for(common = 0; common < baseParts.size() && common < pathParts.size(); common++) {
         if(!PlatformPathEqual(baseParts[common], pathParts[common]))
             break;
     }
 
-    for(int i = common; i < baseParts.size(); i++)
+    for(size_t i = common; i < baseParts.size(); i++)
         resultParts.push_back("..");
 
     resultParts.insert(resultParts.end(),
@@ -732,7 +732,7 @@ static std::string MakePathAbsolute(const std::string &base, const std::string &
 
 static void PathSepNormalize(std::string &filename)
 {
-    for(int i = 0; i < filename.length(); i++) {
+    for(size_t i = 0; i < filename.length(); i++) {
         if(filename[i] == '\\')
             filename[i] = '/';
     }
@@ -742,7 +742,7 @@ static std::string PathSepPlatformToUNIX(const std::string &filename)
 {
 #if defined(WIN32)
     std::string result = filename;
-    for(int i = 0; i < result.length(); i++) {
+    for(size_t i = 0; i < result.length(); i++) {
         if(result[i] == '\\')
             result[i] = '/';
     }
@@ -756,7 +756,7 @@ static std::string PathSepUNIXToPlatform(const std::string &filename)
 {
 #if defined(WIN32)
     std::string result = filename;
-    for(int i = 0; i < result.length(); i++) {
+    for(size_t i = 0; i < result.length(); i++) {
         if(result[i] == '/')
             result[i] = '\\';
     }
diff --git a/src/group.cpp b/src/group.cpp
index f736774..fa70408 100644
--- a/src/group.cpp
+++ b/src/group.cpp
@@ -204,7 +204,7 @@ void Group::MenuGroup(int id) {
             if(pos != std::string::npos)
                 groupName.erase(pos);
 
-            for(int i = 0; i < groupName.length(); i++) {
+            for(size_t i = 0; i < groupName.length(); i++) {
                 if(!(isalnum(groupName[i]) || (unsigned)groupName[i] >= 0x80)) {
                     // convert punctuation to dashes
                     groupName[i] = '-';
diff --git a/src/style.cpp b/src/style.cpp
index c1dd0b2..76cf353 100644
--- a/src/style.cpp
+++ b/src/style.cpp
@@ -35,7 +35,7 @@ std::string Style::CnfWidth(const std::string &prefix) {
 std::string Style::CnfPrefixToName(const std::string &prefix) {
     std::string name = "#def-";
 
-    for(int i = 0; i < prefix.length(); i++) {
+    for(size_t i = 0; i < prefix.length(); i++) {
         if(isupper(prefix[i]) && i != 0)
             name += '-';
         name += tolower(prefix[i]);
diff --git a/tools/unifont2c.cpp b/tools/unifont2c.cpp
index 8def106..7e9bf7a 100644
--- a/tools/unifont2c.cpp
+++ b/tools/unifont2c.cpp
@@ -217,7 +217,7 @@ int main(int argc, char** argv) {
             deflate(&stream, Z_FINISH);
 
             chunk_output_size[chunk_index] += sizeof(compressed_chunk_data) - stream.avail_out;
-            for(int i = 0; i < sizeof(compressed_chunk_data) - stream.avail_out; i += 16) {
+            for(size_t i = 0; i < sizeof(compressed_chunk_data) - stream.avail_out; i += 16) {
                 unsigned char *d = &compressed_chunk_data[i];
                 fprintf(source, "    %3d, %3d, %3d, %3d, %3d, %3d, %3d, %3d, "
                                     "%3d, %3d, %3d, %3d, %3d, %3d, %3d, %3d,\n",