diff --git a/src/callback.c b/src/callback.c
index 7de1337a..a6ef8dcc 100644
--- a/src/callback.c
+++ b/src/callback.c
@@ -266,6 +266,8 @@ static void backannotate_at_cursor_b_pos(xRect *r, Graph_ctx *gr)
       dbg(1, "xx=%g, p=%d\n", xx, p);
       tcleval("array unset ngspice::ngspice_data");
       raw->annot_p = p;
+      raw->annot_x = cursor2;
+      raw->annot_sweep_idx = sweep_idx;
       for(i = 0; i < raw->nvars; ++i) {
         char s[100];
         my_snprintf(s, S(s), "%.4g", raw->values[i][p]);
@@ -403,6 +405,7 @@ static int waves_callback(int event, int mx, int my, KeySym key, int button, int
           }
         } else {
           xctx->raw->annot_p = -1;
+          xctx->raw->annot_sweep_idx = -1;
           /* need_all_redraw = 1; */
           redraw_all_at_end = 1;
         }
diff --git a/src/save.c b/src/save.c
index 0c254f83..91f9a5d9 100644
--- a/src/save.c
+++ b/src/save.c
@@ -383,18 +383,16 @@ void transpose_matrix(double *a, int r, int c)
  * data layout in memory arranged to maximize cache locality 
  * when looking up data 
  */
-static void read_binary_block(FILE *fd, Raw *raw)
+static void read_binary_block(FILE *fd, Raw *raw, int ac)
 {
   int p, v;
   double *tmp;
   int offset = 0;
-  int ac = 0;
 
   if(!raw) {
     dbg(0, "read_binary_block() no raw struct allocated\n");
     return;
   }
-  if(!strcmp(raw->sim_type, "ac")) ac = 1; /* AC analysis, complex numbers twice the size */
 
   for(p = 0 ; p < raw->datasets; p++) {
     offset += raw->npoints[p];
@@ -497,7 +495,7 @@ static int read_dataset(FILE *fd, Raw **rawptr, const char *type)
       if(raw->sim_type) {
         done_header = 1;
         dbg(dbglev, "read_dataset(): read binary block, nvars=%d npoints=%d\n", nvars, npoints);
-        read_binary_block(fd, raw); 
+        read_binary_block(fd, raw, ac); 
         raw->datasets++;
         exit_status = 1;
       } else { 
@@ -775,6 +773,7 @@ int raw_read(const char *f, Raw **rawptr, const char *type)
   raw = *rawptr;
   raw->level = -1; 
   raw->annot_p = -1;
+  raw->annot_sweep_idx = -1;
 
   int_hash_init(&raw->table, HASHSIZE);
   fd = fopen(f, fopen_read_mode);
@@ -842,6 +841,7 @@ int table_read(const char *f)
   raw = xctx->raw;
   raw->level = -1; 
   raw->annot_p = -1;
+  raw->annot_sweep_idx = -1;
 
   /* quick inspect file and get upper bound of number of data lines */
   ufd = open(f, O_RDONLY);
diff --git a/src/token.c b/src/token.c
index d41b9cc0..f8d755f9 100644
--- a/src/token.c
+++ b/src/token.c
@@ -3380,6 +3380,31 @@ static char *get_pin_attr(const char *token, int inst, int s_pnetname)
   return value;
 }
 
+static double interpolate_yval(int idx)
+{
+  double val = xctx->raw->values[idx][xctx->raw->annot_p];
+  /* not operating point, annotate from 'b' cursor */
+  if((xctx->raw->allpoints > 1) && xctx->raw->annot_sweep_idx >= 0) {
+    Raw *raw = xctx->raw;
+    int dset;
+    int npoints;
+    SPICE_DATA *sweep_gv = raw->values[raw->annot_sweep_idx];
+    SPICE_DATA *gv = raw->values[idx];
+    for(dset = 0 ; dset < raw->datasets; dset++) {
+      npoints += raw->npoints[dset];
+      if(npoints > raw->annot_p) break;
+    }
+    if(raw->annot_p + 1 < npoints) {
+      double dx = sweep_gv[raw->annot_p + 1] - sweep_gv[raw->annot_p];
+      double dy = gv[raw->annot_p + 1] - gv[raw->annot_p];
+      double offset = raw->annot_x - sweep_gv[raw->annot_p];
+      double interp = dx != 0.0 ? offset * dy / dx : 0.0;
+      val += interp;
+    }
+  }
+  return val;
+}
+
 /* substitute given tokens in a string with their corresponding values */
 /* ex.: name=@name w=@w l=@l ---> name=m112 w=3e-6 l=0.8e-6 */
 /* if s==NULL return emty string */
@@ -3599,7 +3624,7 @@ const char *translate(int inst, const char* s)
              dbg(1, "translate() @spice_get_voltage: fqnet=%s start_level=%d\n", fqnet, start_level);
              idx = get_raw_index(fqnet);
              if(idx >= 0) {
-               val = xctx->raw->values[idx][xctx->raw->annot_p];
+               val = interpolate_yval(idx);
              }
              if(idx < 0) {
                valstr = "";
@@ -3656,7 +3681,7 @@ const char *translate(int inst, const char* s)
            dbg(1, "translate(): net=%s, fqnet=%s start_level=%d\n", net, fqnet, start_level);
            idx = get_raw_index(fqnet);
            if(idx >= 0) {
-             val = xctx->raw->values[idx][xctx->raw->annot_p];
+             val = interpolate_yval(idx);
            }
            if(idx < 0) {
              valstr = "";
@@ -3724,7 +3749,7 @@ const char *translate(int inst, const char* s)
            dbg(1, "fqdev=%s\n", fqdev);
            idx = get_raw_index(fqdev);
            if(idx >= 0) {
-             val = xctx->raw->values[idx][xctx->raw->annot_p];
+             val = interpolate_yval(idx);
            }
            if(idx < 0) {
              valstr = "";
@@ -3784,19 +3809,13 @@ const char *translate(int inst, const char* s)
            dbg(1, "translate(): fqnet1=%s start_level=%d\n", fqnet1, start_level);
            dbg(1, "translate(): fqnet2=%s start_level=%d\n", fqnet2, start_level);
            idx1 = get_raw_index(fqnet1);
-           if(idx1 >= 0) {
-             val1 = xctx->raw->values[idx1][xctx->raw->annot_p];
-           }
            idx2 = get_raw_index(fqnet2);
-           if(idx2 >= 0) {
-             val2 = xctx->raw->values[idx2][xctx->raw->annot_p];
-           }
-           val = val1 - val2;
            if(idx1 < 0 || idx2 < 0) {
              valstr = "";
              xctx->tok_size = 0;
              len = 0;
            } else {
+             val = interpolate_yval(idx1) - interpolate_yval(idx2);
              valstr = dtoa_eng(val);
              len = xctx->tok_size;
            }
@@ -3856,7 +3875,7 @@ const char *translate(int inst, const char* s)
          strtolower(fqdev);
          idx = get_raw_index(fqdev);
          if(idx >= 0) {
-           val = xctx->raw->values[idx][xctx->raw->annot_p];
+           val = interpolate_yval(idx);
          }
          if(idx < 0) {
            valstr = "";
diff --git a/src/xschem.h b/src/xschem.h
index 9096c733..5fb0106e 100644
--- a/src/xschem.h
+++ b/src/xschem.h
@@ -774,7 +774,12 @@ typedef struct {
   int datasets;
   Int_hashtable table;
   const char *sim_type; /* type of sim, "tran", "dc", "ac", "op", ... */
-  int annot_p; /* point in raw file to use for annotating schematic voltages/currents/etc */
+  int annot_p; /* point in raw file to use for annotating schematic voltages/currents/etc
+                * this is the closest available simulated point *before* the point
+                * calculated from mouse in graph */
+  double annot_x; /* X point to backannotate as calculated from mouse position.
+                   * need to interpolate the Y value between annot_p and annot_p + 1 */
+  int annot_sweep_idx; /* index of sweep variable where cursor annotation has occurred */
   /* when descending hierarchy xctx->current_name changes, xctx->raw_schname
    * holds the name of the top schematic from which the raw file was loaded */
   char *schname;