diff --git a/Makefile b/Makefile
index 48fb8db7..9346e33f 100644
--- a/Makefile
+++ b/Makefile
@@ -9,16 +9,13 @@ TARGET ?= unix
 
 ifeq ($(TARGET),unix)
 # Regular *nix system.
-SIZE = size
 
 else ifeq ($(TARGET),pca10040)
 # PCA10040: nRF52832 development board
-SIZE = arm-none-eabi-size
 OBJCOPY = arm-none-eabi-objcopy
 TGOFLAGS += -target $(TARGET)
 
 else ifeq ($(TARGET),arduino)
-SIZE = avr-size
 OBJCOPY = avr-objcopy
 TGOFLAGS += -target $(TARGET)
 
@@ -68,13 +65,11 @@ build/tgo: *.go
 
 # Binary that can run on the host.
 build/%: src/examples/% src/examples/%/*.go build/tgo src/runtime/*.go
-	./build/tgo build $(TGOFLAGS) -o $@ $(subst src/,,$<)
-	@$(SIZE) $@
+	./build/tgo build $(TGOFLAGS) -size=short -o $@ $(subst src/,,$<)
 
 # ELF file that can run on a microcontroller.
 build/%.elf: src/examples/% src/examples/%/*.go build/tgo src/runtime/*.go
-	./build/tgo build $(TGOFLAGS) -o $@ $(subst src/,,$<)
-	@$(SIZE) $@
+	./build/tgo build $(TGOFLAGS) -size=short -o $@ $(subst src/,,$<)
 
 # Convert executable to Intel hex file (for flashing).
 build/%.hex: build/%.elf
diff --git a/binutils.go b/binutils.go
new file mode 100644
index 00000000..bb83c872
--- /dev/null
+++ b/binutils.go
@@ -0,0 +1,160 @@
+package main
+
+import (
+	"debug/elf"
+	"sort"
+	"strings"
+)
+
+// Statistics about code size in a program.
+type ProgramSize struct {
+	Packages map[string]*PackageSize
+	Sum      *PackageSize
+	Code     uint64
+	Data     uint64
+	BSS      uint64
+}
+
+// Return the list of package names (ProgramSize.Packages) sorted
+// alphabetically.
+func (ps *ProgramSize) SortedPackageNames() []string {
+	names := make([]string, 0, len(ps.Packages))
+	for name := range ps.Packages {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
+// The size of a package, calculated from the linked object file.
+type PackageSize struct {
+	Code   uint64
+	ROData uint64
+	Data   uint64
+	BSS    uint64
+}
+
+// Flash usage in regular microcontrollers.
+func (ps *PackageSize) Flash() uint64 {
+	return ps.Code + ps.ROData + ps.Data
+}
+
+// Static RAM usage in regular microcontrollers.
+func (ps *PackageSize) RAM() uint64 {
+	return ps.Data + ps.BSS
+}
+
+type symbolList []elf.Symbol
+
+func (l symbolList) Len() int {
+	return len(l)
+}
+
+func (l symbolList) Less(i, j int) bool {
+	bind_i := elf.ST_BIND(l[i].Info)
+	bind_j := elf.ST_BIND(l[j].Info)
+	if l[i].Value == l[j].Value && bind_i != elf.STB_WEAK && bind_j == elf.STB_WEAK {
+		// sort weak symbols after non-weak symbols
+		return true
+	}
+	return l[i].Value < l[j].Value
+}
+
+func (l symbolList) Swap(i, j int) {
+	l[i], l[j] = l[j], l[i]
+}
+
+// Calculate program/data size breakdown of each package for a given ELF file.
+func Sizes(path string) (*ProgramSize, error) {
+	file, err := elf.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	var sumCode uint64
+	var sumData uint64
+	var sumBSS uint64
+	for _, section := range file.Sections {
+		if section.Flags&elf.SHF_ALLOC == 0 {
+			continue
+		}
+		if section.Type != elf.SHT_PROGBITS && section.Type != elf.SHT_NOBITS {
+			continue
+		}
+		if section.Type == elf.SHT_NOBITS {
+			sumBSS += section.Size
+		} else if section.Flags&elf.SHF_EXECINSTR != 0 {
+			sumCode += section.Size
+		} else if section.Flags&elf.SHF_WRITE != 0 {
+			sumData += section.Size
+		}
+	}
+
+	allSymbols, err := file.Symbols()
+	if err != nil {
+		return nil, err
+	}
+	symbols := make([]elf.Symbol, 0, len(allSymbols))
+	for _, symbol := range allSymbols {
+		symType := elf.ST_TYPE(symbol.Info)
+		if symbol.Size == 0 {
+			continue
+		}
+		if symType != elf.STT_FUNC && symType != elf.STT_OBJECT && symType != elf.STT_NOTYPE {
+			continue
+		}
+		if symbol.Section >= elf.SectionIndex(len(file.Sections)) {
+			continue
+		}
+		section := file.Sections[symbol.Section]
+		if section.Flags&elf.SHF_ALLOC == 0 {
+			continue
+		}
+		symbols = append(symbols, symbol)
+	}
+	sort.Sort(symbolList(symbols))
+
+	sizes := map[string]*PackageSize{}
+	var lastSymbolValue uint64
+	for _, symbol := range symbols {
+		symType := elf.ST_TYPE(symbol.Info)
+		//bind := elf.ST_BIND(symbol.Info)
+		section := file.Sections[symbol.Section]
+		pkgName := "(bootstrap)"
+		symName := strings.TrimLeft(symbol.Name, "(*")
+		dot := strings.IndexByte(symName, '.')
+		if dot > 0 {
+			pkgName = symName[:dot]
+		}
+		pkgSize := sizes[pkgName]
+		if pkgSize == nil {
+			pkgSize = &PackageSize{}
+			sizes[pkgName] = pkgSize
+		}
+		if lastSymbolValue != symbol.Value || lastSymbolValue == 0 {
+			if symType == elf.STT_FUNC {
+				pkgSize.Code += symbol.Size
+			} else if section.Flags&elf.SHF_WRITE != 0 {
+				if section.Type == elf.SHT_NOBITS {
+					pkgSize.BSS += symbol.Size
+				} else {
+					pkgSize.Data += symbol.Size
+				}
+			} else {
+				pkgSize.ROData += symbol.Size
+			}
+		}
+		lastSymbolValue = symbol.Value
+	}
+
+	sum := &PackageSize{}
+	for _, pkg := range sizes {
+		sum.Code += pkg.Code
+		sum.ROData += pkg.ROData
+		sum.Data += pkg.Data
+		sum.BSS += pkg.BSS
+	}
+
+	return &ProgramSize{Packages: sizes, Code: sumCode, Data: sumData, BSS: sumBSS, Sum: sum}, nil
+}
diff --git a/main.go b/main.go
index 4312ea4a..79dd340b 100644
--- a/main.go
+++ b/main.go
@@ -16,7 +16,7 @@ import (
 )
 
 // Helper function for Compiler object.
-func Compile(pkgName, outpath string, spec *TargetSpec, printIR, dumpSSA bool, action func(string) error) error {
+func Compile(pkgName, outpath string, spec *TargetSpec, printIR, dumpSSA bool, printSizes string, action func(string) error) error {
 	c, err := NewCompiler(pkgName, spec.Triple, dumpSSA)
 	if err != nil {
 		return err
@@ -97,6 +97,25 @@ func Compile(pkgName, outpath string, spec *TargetSpec, printIR, dumpSSA bool, a
 			return err
 		}
 
+		if printSizes == "short" || printSizes == "full" {
+			sizes, err := Sizes(executable)
+			if err != nil {
+				return err
+			}
+			if printSizes == "short" {
+				fmt.Printf("   code    data     bss |   flash     ram\n")
+				fmt.Printf("%7d %7d %7d | %7d %7d\n", sizes.Code, sizes.Data, sizes.BSS, sizes.Code+sizes.Data, sizes.Data+sizes.BSS)
+			} else {
+				fmt.Printf("   code  rodata    data     bss |   flash     ram | package\n")
+				for _, name := range sizes.SortedPackageNames() {
+					pkgSize := sizes.Packages[name]
+					fmt.Printf("%7d %7d %7d %7d | %7d %7d | %s\n", pkgSize.Code, pkgSize.ROData, pkgSize.Data, pkgSize.BSS, pkgSize.Flash(), pkgSize.RAM(), name)
+				}
+				fmt.Printf("%7d %7d %7d %7d | %7d %7d | (sum)\n", sizes.Sum.Code, sizes.Sum.ROData, sizes.Sum.Data, sizes.Sum.BSS, sizes.Sum.Flash(), sizes.Sum.RAM())
+				fmt.Printf("%7d       - %7d %7d | %7d %7d | (all)\n", sizes.Code, sizes.Data, sizes.BSS, sizes.Code+sizes.Data, sizes.Data+sizes.BSS)
+			}
+		}
+
 		if strings.HasSuffix(outpath, ".hex") {
 			// Get an Intel .hex file from the .elf file.
 			tmppath = filepath.Join(dir, "main.hex")
@@ -112,13 +131,13 @@ func Compile(pkgName, outpath string, spec *TargetSpec, printIR, dumpSSA bool, a
 	}
 }
 
-func Build(pkgName, outpath, target string, printIR, dumpSSA bool) error {
+func Build(pkgName, outpath, target string, printIR, dumpSSA bool, printSizes string) error {
 	spec, err := LoadTarget(target)
 	if err != nil {
 		return err
 	}
 
-	return Compile(pkgName, outpath, spec, printIR, dumpSSA, func(tmppath string) error {
+	return Compile(pkgName, outpath, spec, printIR, dumpSSA, printSizes, func(tmppath string) error {
 		if err := os.Rename(tmppath, outpath); err != nil {
 			// Moving failed. Do a file copy.
 			inf, err := os.Open(tmppath)
@@ -146,13 +165,13 @@ func Build(pkgName, outpath, target string, printIR, dumpSSA bool) error {
 	})
 }
 
-func Flash(pkgName, target, port string, printIR, dumpSSA bool) error {
+func Flash(pkgName, target, port string, printIR, dumpSSA bool, printSizes string) error {
 	spec, err := LoadTarget(target)
 	if err != nil {
 		return err
 	}
 
-	return Compile(pkgName, ".hex", spec, printIR, dumpSSA, func(tmppath string) error {
+	return Compile(pkgName, ".hex", spec, printIR, dumpSSA, printSizes, func(tmppath string) error {
 		// Create the command.
 		flashCmd := spec.Flasher
 		parts := strings.Split(flashCmd, " ") // TODO: this should be a real shell split
@@ -216,6 +235,7 @@ func main() {
 	printIR := flag.Bool("printir", false, "print LLVM IR")
 	dumpSSA := flag.Bool("dumpssa", false, "dump internal Go SSA")
 	target := flag.String("target", llvm.DefaultTargetTriple(), "LLVM target")
+	printSize := flag.String("size", "", "print sizes (none, short, full)")
 	port := flag.String("port", "/dev/ttyACM0", "flash port")
 
 	if len(os.Args) < 2 {
@@ -241,7 +261,7 @@ func main() {
 			usage()
 			os.Exit(1)
 		}
-		err := Build(flag.Arg(0), *outpath, *target, *printIR, *dumpSSA)
+		err := Build(flag.Arg(0), *outpath, *target, *printIR, *dumpSSA, *printSize)
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "error:", err)
 			os.Exit(1)
@@ -252,7 +272,7 @@ func main() {
 			usage()
 			os.Exit(1)
 		}
-		err := Flash(flag.Arg(0), *target, *port, *printIR, *dumpSSA)
+		err := Flash(flag.Arg(0), *target, *port, *printIR, *dumpSSA, *printSize)
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "error:", err)
 			os.Exit(1)