HRM Accuracy

Everything is an estimate, even an HRM. It's just a better estimate! Could you burn that many calories? Sure. If I ride my bike for 3 1/2 hours, I can burn 1500 calories. I have switched to the TDEE - 20% method. You base your calorie intake on your weekly activity level including exercise, and don't eat back any exercise calories. I like it better as I eat the same amount of calories each day.

Are you able to look at what your average heart rate was on your HRM? If you can you can use a few other calories-burned-heartrate websites to calculate how many calories were burned and see if the numbers seem more or less close. I'd check that and then if your HRM calculation is way off then there is probably something set wrong or it's got an issue. I always used this site once I did a workout with my HRM:
http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx

Not saying it's exactly accurate but I used this method when I was tracking food/calories burned and I was consistently loosing weight so I guess it was close enough.

As far as eating back those calories...if you're actually burning that much, then I'd try to eat back what I could (and it's fine to try another method as the other person suggested where you don't have 'eat back' calories as long as you know you are getting enough cals during the day). You might need to invest in some calorie dense snacks to keep around like dried fruit or nuts, nut butters, or avocados. Ha, let yourself have more butter/oil if you want.
I used to keep dried cherries and walnuts on hand to munch if I was low on cals....good for you but a good calorie punch. And that way you don't have to eat A LOT of food to get a good amount of calories.

It will grossly overestimate when you did the lifting, because it only goes off your heart rate, not what you're actually doing. I could wear it while my child has a tantrum, or during a scary movie, and though my heart rate is skyrocketing I'm not actually running a marathon, so I didn't burn 70 cals just listening to a toddler tantrum. I can make my heart rate rise just thinking scary thoughts (try it, it's fun) but it isn't burning. Weights are the same way - your heart rate will be doing one thing, but the calorie burn from weights comes during repair. So don't wear it for that. It gives huge numbers. They monitor steady-state cardio - ie: you're doing the same cardio-ish thing for a period of time. You can google 'heart rate monitor and strength training' for a more sciency answer.

Also ensure you've set it to your own base heart rate. Mine was set at a base of 60 bpm, and told me I burned a bajillion calories during exercise because, to the machine, me going from 60 up to 100 was a leap of 40. However my base rest rate is actually 85-90 - no, I've no idea why - so going up to 100 wasn't really that epic at all. Once I'd set the base rate properly, it gave a lower calorie burn for my cardio, but the numbers all match up for weight loss/gain/maintain so chances are they're correct.

Running and hiking give me dead good numbers. 249 cals this morning doing C25K #2, 350 on an hour's hike, sounds similar to my figures. We're a similar size. So, the lifts aside, it's probably right.

c25k is a 30 minute program of running and walking; assume you went 2.5 to 2.7 miles, so 250 to 270 calories. The dog walk add 100 calories for each mile, assume 3. So 300 calories. The weight lifting depends on what you did; heavy strenuous compound lifting or what? So far, 550 to 570 calories as estimates. Lifting burns less calories then running, and HRM ought to be used for steady state cardio to provide an estimate. You didn't burn 1400 plus calories.

They are not accurate for lifting weights. Only use them for steady cardio like running and biking or whatever else where your heart rate isn't jumping and falling rapidly.

I'd also recommend taking 10% off what it says just to be safe because they aren't 100% accurate, just the closest you can get. It's what I do at least

But if this is true than what good is a heart rate monitor? I was under the assumption that a HRM would give me a more accurate picture of what I was burning.

It does, for cardio. No electric doohicky can gauge the calories of strength training. It's why people are still arguing about how much strength training actually burns (some say 'nothing!', others says 'millions!', and others have the data - training done versus weight lost - that shows it's 'quite considerable if you work hard'.)

Your HRM isn't going to be of any use for calorie burn during weight training...it is only relatively accurate for a steady state aerobic event. Also, if you are out of shape, your HR is going to be higher than someone who is in shape...most of these are calibrated using statistical averages of fit individuals...so your higher HR is going to artificially inflate your calorie burn. As you get more fit, your monitor will be more accurate. Even then, it's an estimate and you'd at minimum want to knock off your basal calories.

When I was doing the MFP eat back method I knocked off around 20% from whatever my HRM told me for a steady state aerobic event....I never used it for weight training because it is pretty much worthless for that activity as I stated before.

Also, while your number is somewhat inflated, you probably did burn quite a few calories...that's a lot of exercise. You have to begin to understand the relationship between your activity and your calorie requisites. When I'm training for a cycling event for example, I often need around 3,000 calories...and that's to keep my rate of loss at around 0.5 - 1 Lb per week. This is where a lot of people go wrong...they think they have to do all of this exercise and whatnot but don't understand how to properly fuel their bodies.